EDIT: ahh, beat me to it Jabalac
I like the idea of Myr tribal a lot, and your deck looks pretty solid. If you want to keep to the tribal + equipment theme,
Stoneforge Masterwork would be a perfect card for the job. The more Myr you have, the more buff it gives
On the Myr front, getting a little more muscle in the form of
Lodestone Myr or
Myr Enforcer could go a long way to closing out games.
Lodestone Myr is especially nice with
Myr Galvanizer, since you can tap everything to buff him, then use Galvanizer to untap everything... then tap them again!
Finally, having a way to get back your best cards is important, so maybe run a couple copies of
Myr Retriever to get back that Galvinizer your opponent Lightning Bolted.
To make room for these (4
Stoneforge Masterwork, 2
Lodestone Myr, 2
Myr Enforcer, 2
Myr Retriever), I'd probably cut the 2
Avarice Amulet (not a bad card, but Stoneforge Materwork just does what you want to be doing better), and 2 of the 3
Pennon Blade (same reason, Stoneforge does basically the same thing for WAY less mana). Then for creatures, since your equip costs are so much lower without the Amulet or Blade, you could probably cut the 2 Brass Squires.
Darksteel Myr is a great blocker, but so is
Myr Enforcer, and with affinity, I think it's actually more powerful, so you could probably cut those as well. Finally, for the last two slots... I'm really not sure, I want to say
Myr Superion, just because there are cases where it can get stranded in your hand, but it's power level is just so high it would be a hard cut. Maybe just cut 1 and only run a single
Myr Enforcer? In the end, it's totally up to you since it's your deck.
At the very least, I hope this gives you something to think about, and if you have any other questions, please feel free to ask!