I'm grateful that Sticker Mule provides designers to aid process. It maybe more helpful and efficient, if you could provide a template on your site so on artwork upload (for buttons, stickers etc.) one can immediately see, if more bleed is required.
It would be awesome to always have available predesigned stickers (like you are already doing from time to time at an amazing price) someting like a Deals page or Store where you are always selling new packs ^^
Maybe also different types, like gaming, developers, designers, etc.
Make it possible to design, and edit your own logo from your website. Sure using your professionals is fantastic, but it would be helpful to be able to create a design yourself to give the professional something to start with.