Your first idea isn't far off. I've worked with some mixed-media artists to do similar things, and here are some ideas that you might want to play with (note that these options require a darkroom, and/or some special equipment, and they can all be a bit fiddly - it takes practice to get usable results.):
Liquid Photographic Emulsion (B&W)
One option I've had success with is coating the original surface with a product called Liquid Light from Rockland Colloid. This is basically the silver-flavored Jell-O (the gelatin emulsion that goes on black-and-white photographic paper) in a black bottle.
I won't go too far into detail because there are lots of places that give you the details - basically melt it in the darkroom, coat your material in it, let it dry in the dark, then expose and process like you would a regular sheet of photo paper. When I've used this process we usually do the photo part first (applying the emulsion to a gesso'd canvas for instance), but your idea of coating the final piece with resin and over-printing could work too.
The caveat with liquid light is that you have to use and process it like regular photo paper. This means it's not a good fit if:
- Your material is highly textured
You may not be able to stop down an enlarger enough to get the print in focus on a textured surface.
- Your material can't get wet, or can't tolerate darkroom chemicals
You need to put darkroom chemicals on the emulsion to process it. That means water.
Polaroid processes (Color or B&W)
Polaroid may be dead, but their process lives on, and it's a good way to manipulate images.
Basically acquire some Fuji peel-apart film (FP-100C for color, FP-3000B for black-and-white) in an appropriate size -- it's available up to 8x10 -- and use it to make your image. The "how" here is left as an exercise for the reader - I've used Polaroid backs for cameras, a Daylab (basically a slide enlarger that works with the Polaroid film), and even a regular B&W enlarger and a rolling pin (to press the film and process it).
You have two options in the Polaroid family -- the first is making an image transfer onto your final medium (Quick-and-Dirty: peel the film apart early in its processing and mash the "negative" side against the surface of your other material while it processes. This works best for porous stuff like paper).
The other Polaroid option is an emulsion lift, where you process the instant film until it's done, then soak the print until the image lifts off the paper (it's basically a floating jelly-like sheet that you can then lay onto pretty much any other surface).
The emulsion lift sounds promising, especially as you'd be able to lay it directly on a textured surface, but they are fragile and fiddly things while they're wet (and once dry they need some protection, like shellac, or they can be easily damaged and flake off).
