Wow, XinTek isn't bad at all :P About the shop, the plural of signature is signatures. No ' before the s. Same for logos, avatars and desktop backgrounds.
For desktop backgrounds, you should make something Toribash related; not many people would buy them otherwise.
On the prices:
Avatar and signature prices are fine.
For logos, I'd say lower it a little; 1.5k through 2.5k maybe.
Desktop backgrounds, I don't think anyone would buy them as of now..1k through 5k.