I have covered at least 10 pieces in this epoxy resin, and I love the results. It looks like glass or 50 coats of varnish. I took the time to learn how to do it right, both by watching all the YouTube videos demonstrating it and watching an artist friend of mine do it in person (and her pieces sell for thousands!). It works well on mounted wooden panels. If you want to use it on canvas, wrap the canvas around a wooden panel (just like you would stretch canvas over bars) and staple into the back.
You will need a mask for the fumes (I feel like Darth Vader when I'm wearing it), rubber gloves, a heat gun (this helps get out the bubbles), two paper mixing buckets and a big paint stir stick, two clear plastic "party" cups (I use ones with stripes to help me with the measuring), shims and a level, a toothpick to get out bits of dust from the surface while it's wet, and a cheap chip brush or foam brush to spread it around. I use painter's tape on the bottom of the piece to make it easier to remove the drips without having to sand them off (I remove the tape after about 4 hours, before everything's really hardened, but the pieces are still tacky at this point, so it's a tricky operation). I also elevate the pieces so they're not sitting in the dripped off resin. A cheap plastic tablecloth will protect your work surface, and the dried resin will peel right off it.
So many of the materials (gloves, buckets, cups, stick, and brush) all have to be thrown away afterwards, that it's better to do several projects at once, although not more than you can manage in the time frame before it starts to set. A large cardboard box or a clear plastic container should be set over the finished piece for the first two days while it dries. Dust and little hairs are your worst enemy when using this process, so try to do it in a low-dust environment, and use a strong light to check the surface for the little buggers while it's still wet.
I have done this successfully over photographs, but I have to seal the photos first (this also works with paper). I messed up a few before I figured out the best way to do this. I mount the photos on a painted wooden panel with spray glue, then I spray the picture with fixative, which seems to help protect it. Then I spray on a clear acrylic finish. Then I paint on clear acrylic gloss medium (which is like varnish). I used to go straight from the glue stage to the gloss medium, but that's when I would run into trouble getting the picture too wet and smeared. The two steps in between have eliminated any problems with that. Be sure to allow the piece to dry thoroughly after each step. The gloss medium might not be necessary, since I've used the spray acrylic, but I'm going for a thick, deep, shiny effect.
Anyway, once you get the hang of the process, you will be eager to try it on everything! I looked at this item in art supply stores, but Amazon has the best price.