Can I put an image on the front and back of a t-shirt?
Yes but whatever you put on the front will become the default preview image. If you just use a small pocket logo there, the preview will be useless, so I put "2 Sided" prominently in the title so there's a chance they'll look more closely and see the large image on the back. These do not sell for me unless I also do the same shirt with the large design on front so that maybe sometimes in a search, the two will appear side by side and people will see them both and go "ah, that's the one I want."
If you print on the back only, that will be the default that people see. If someone from Merch is reading this, we need the ability to specify which image to show people by default.