i can't see your picture!
if you want something 'big' (i assume you mean interesting) you probably don't want (plain) terezi or vriska. damara is the *most* interesting costume (in my opinion) out of these.
-vriska with a really really awesome detailed roboarm
-mindfang (pirate outfit <3)
-latula's outfit is pretty interesting, and she's my favorite
-a genderbent mituna (oh but if you get really.. slutty with it you might get dirty looks from homestuckers lol. i would personally do latula's outfit, with mituna's designs if that makes sense. if you like that idea ^^)
the last 4 are au's. the designs are really pretty!! it would be really unique too.