Disclaimer: The following description was written for the non-budget version, so there might be cards not listed in this one and viceversa. Moreover, this version is budget based on the cards I already own, the most expensive ones being Damnation and Kindred Discovery. The cost, for me, is about € 75.

Explain the deck

Introduction

This is NOT a Sliver Tribal, and I think it's pretty obvious. This is a janky build for a powerful commander. It's primary purpose is to have fun.
Since I started playing Magic, back when Shadowmoor/Lorwyn was just released, I've always liked playing with creature types, and that's exactly what this deck wants to do. There's a lot of cards that can change creature types like Unnatural Selection, and then there's a lot of powerful effect like Undead Slayer, ready to take advantage of that.
There are also some lords that do not specify "you control" such as Field Marshal. This way you can give +1/+1 and first strike to a creature your opponent control (saving that creature from an unfavorable block, for example) to make a deal with them. The same goes with Necrotic Sliver, which will let you make deals such as "Use that creature (that's annoying to me) to destroy that permanent that's annoying to you". You just have to tap your Imagecrafter.

How to play the deck

This deck is a political deck. Not exactly a group hug, but you should make deals with your opponent throughout the game. And please, do not betray the deals you make. That's mean.

With that out of the way, let's talk about what you should be doing at every stage of the game. In the early game, lay low by only playing some non-threatening changelings and try not to mess too much with your opponents' stuff. Wait until you find some type-changing card like Unnatural Selection or Imagecrafter and some Tribe Lords. That's the point when you can start doing all your fun stuff, but always remeber to BE POLITICAL!! Ask other players if they like what you're gonna do and if not try to deal with them in order to take advantage over them little by little.
When late game approaches, you should have established your dominion over all creatures, and you should use that to try to close the game by playing threatening cards like Utvara Hellkite, Gilt-Leaf Archdruid, Sliver Legion. Play these cards only when you are pretty sure they are not gonna instantly blown away, cause there aren't a lot of finishers in this deck, and winning only with changelings it's gonna be pretty hard.

Now, there's one more question I have to answer: when should you play the commander?
In general, do not play your commander until it's safe to do so. Also, note that your commander is not essential to the strategy of the deck. It certainly supports it, but there will be games where you will not even need to play the Overlord.
Anyway, if you're having trouble finding a tribe-changing card, then you can play Sliver Overlord in order to grab Amoeboid Changeling, which, in my opinion, is by far one of the strongest cards in the entire deck. Only in this case you should play your commander even if it is not protected.
Also, remember you can use his second ability to steal other player's best creatures, but keep in mind that if you do so, you will be hated by everyone at the table, you will be the Archenemy, so use this power wisely.

Sinergies:

• Merrow commerce + Undead Slayer / Merfolk Sovereign / Gilt-Leaf Archdruid / Imagecrafter / Amoeboid Changeling / Gemhide Sliver / Manaweft Sliver

• Grim Captain's Call + tribal non-creature cards. (for the same reason I want to add Lord of the Undead and maybe even Ashes of the Fallen)

• I'm also thinking about substitute Sliver Hivelord and Chromatic Lantern with Timber Protector, and Dryad of the Ilysian Grove, in order to make all my lands indestructible, even though usually my playgroup does not play Armageddon effects.

Notes on Specific Cards

Arcane Adaptation: With Arcane Adaptation you can choose one of the following creature types: Sliver (7 + commander), Merfolk (2), Druid (1), Knight (1), Soldier (1), Illusion (1), Dragon (2), Scarecrow (1). The number between ( ) represents the number of cards that care about that creature type. There's no correct way to choose, it depends on the game state. The safer choice is Sliver, since you can use the first ability of Sliver Overlord to tutor for whatever creature you may need, but if you have Lord of the Unreal in your hand or play, you should really take into consideration to choose Illusion, since the lord will grant hexproof to all your creatures, including himself. There's a lot of possible situations, so try experimenting new things!

Shields of Velis Vel / Mirror Entity: these extremely powerful cards share the same effect: they give ALL creature type to ALL your creatures. Use them to surprise your opponents, and imagine your Field Marshal becoming an Eldrazi Ooze Homarid Kobold Werewolf Kithkin Faerie Elf Shade Zombie Dinosaur all at once. On top of that, Shields of Velis Vel can even be used on your opponents creatures to save or pump them to maintain alliances.

Conclusion

Many of you may ask why don't I play that specific card or that specific tribe. That's probably simply because I was not able to find it, so please, tell me if you know powerful cards that could be in this deck! There's a hell lot of tribes and it's literally impossible for me to search all of them for useful cards.
Also, feel free to take and change this deck, but please let me know if you do that, I will gladly look at the changes you make!
The deck will play a lot differently if you change the lords, so try to do that and let me know what you think.
Thanks for reading all this through and enjoy your commander!

Honorable Mentions:

• rakdos, the showstopper: it introduces a chaos theme which I am not very enthusiast with, but it fits perfectly the strange tribe requirements.
• rebel informer: additional removal against graveyard-based decks.
• haakon, stromgald scourge: I would really, really love to play this card in the deck, but unfortunately it is not possible, since I don't have any way, apart from Pull from Tomorrow, to have Haakon go into the graveyard.
• myr galvanizer, intruder alarm + captivating vampire, voice of the woods, patron wizard, gravespawn sovereign, ... you can find more of these creatures here