Funny... when I was just there in Feb, I don't remember seeing the Build-Your-Own @ Chapeau in MK. They do the embroidery and had a huge selection, but I didn't see the parts/pieces.
However, I DID see them @ Downtown Disney in the other side of The Art of
Disney store (where they have scrapbooking stuff, art supplies and the like). I have no pictures, but lemme see if I can remember...
Ears:
Gold & Silver, Black with lights, pink fuzzy, black, red, Minnie, pink, purple, glittery (pink & white), green, white bridal, satin black.... seems like there was another color of fuzzy - maybe white?
Hat bases:
Red polka dot, Steamboat Willie, Standard black, Mickey pants, green, pink, purple, princessie, bridal..... seems like there were more! I can't remember!
Some of the hats also had places to add stuff like lights or tiaras or characters and whatnot.
Hope that helps!