I'd enjoy some features that'd really improve an experience from someone who commissions art:
1. An option to upload art that has been commissioned by the user with full crediting to the original artist, so the site can still effectively be used as an image gallery to quickly link to without disparaging content creators with art theft or lack of attributing.
2. A better, well versed commissioning section of the art portal. Dedicated pricing, customer rating systems, authentication, etc. No 'Pay in Exposure'. This will ensure that artists can post commission rates and commissioners can easily find artists to pay.
3. More tags per picture. Four is just simply not enough.
4. A moderated Collaboration portal. A lot of the ads seem illicit at times, but that may just be me.