As a merchant :
Top Selling and Top Search Reports - would be nice to be able to remove items no longer listed. Or remove those features if not used that much.
Demos - have the demo uploaded to the main item's page instead of having them on 2 separate pages.
Ability to customise store fronts pages
Bigger profile pics and banners.
As a customer :
Favoriting Stores
Having subcategories for our favorites' list. example; shoes, furniture, etc.
Have other "Sort by" options like mesh, colour, texture, size, etc. IDK i just threw that in randomly.
Like Charlotte said ; Redelivery button !!!