Some things I'd love to see:
A storefront profile to showcase the items you've created.
Customer Ratings - Purchasers rate you
Item Ratings - Purchasers rate the items they purchase
Here's some examples:
Some kind of mechanism put in place to allow people to co-create and split up funds.
If someone has an issue - instead of emailing you directly they can write a support ticket you can then answer.
For example: this was made for Unreal Tournament - maybe even limit its usage to only be used in UT.
Many of the other online marketplaces have these features and I'm sure they are "in the works" but yeah it'd be nice to have! Any other ideas on how they might improve the marketplace?