Given your commander's ability, I would focus more on having your permanents survive the board wipe. Indestructible on anything is an argument for having it in your deck. Another useful, and often overlooked ability is phasing, although for this case you want control over the effect. Look at
Vanishing,
Vodalian Illusionist, and maybe
Warping Wurm. Finally, look for permanents with leaves-play or goes-to-the-graveyard triggered effects. If those effects put creatures or other permanents into play then you will again be starting ahead of the game after the board wipe. While some sacrifice effects will at least allow you to get something out of your permanents before the wipe, if they just put another permanent into play, the timing of effects means that you'll just lose it in the wipe. So the effect of something like
Centaur's Herald isn't going to help you get that fast restart after the wipe.
In general, while there are some cards you're just going to put in any Commander deck of the right colors (I'm looking at you,
Vampire Nighthawk) you want to
concentrate on cards with synergies with your Commander's abilities. Your big advantage when playing
Child of Alara is that you know the board wipe is coming and can prepare for it. Don't just look for good cards--look for good cards that work well with your Commander.