They look like tiles from a mobster's mansion to me.

 Exactly! The Diablo reference is ideal for this, in my opinion.

But hey, these are way too nice to just throw them away!
Maybe you can give them another use? If you differentiate them with colours, you can use them (as you said) as tribe's emblems or something..

But yeah, they are too abstract to represent a specific feat.

Good job nonetheless :)

Now I know exactly what you mean. I remember something like this in diablo. They had quest icons that were silhouette and when one was completed the dim area would burst in a flame and reveal its more visible image.

dark silhouette meaning a solid black (or dark gray) shape of the item in question, such as a sword or a symbol or whatever it is.  It hints at something but because it's all black you can't tell what it is.  Once it's unlocked you take that shape and fill it in with the sprite.  I'd link an example but have spotty internet at the moment...

Well, looks like im junking thisand going back to simplicity

Can you explain a dark silhouette.Not sure what it means. I think your right as far as reading these well as achievements. My other consideration was making these crests to go with different gangs, clans, tribes or demi gods. What do you think, I really like the geometric patterns and would hate to scratch this. Im working on a rpg game based off of a  D&D fill. I love the old nentendo games final fantasy style and zelda art and thats what im going for.Would love your insight.

I don't see these reading well as symbols for achievements and what-not, even if they were all colored like the one in the preview file.  If they represent unlocked achievements, generally you'll at least see a dark silhouette of the eventual shape.

But I do like the muted palette, and they'd probably work well with a solid symbol drawn over them (like swords and arrows and daggers).  Either way this is at least pleasant to look at.  For some reason I thought of a menu background screen before reading your description.