I simply buy heavy metal sheet plates (construction tie down plates that get put into concrete) are only a couple of bucks each.
Find a design you like - trace it on to the metal plate with a sharpie and simply cut it out with a metal cutting blade ( or 3) with a jigsaw cutter.
Drill a couple of mounting holes to attach to the gamo target mechanism and you are done .....
Bats, Birds, objects, you are only limited by your own imagination.
Add a decent spring to the back and you can hang your target upside-down or at a sideways angle so that it either snaps to the side or up on itself when shot -
perfect for BATS , woodpeckers etc or other tree dwelling creatures.
just do a google search for 'Field target faceplate designs' and you'll find tons of good ideas.
My kids LOVE shooting Sidewalk Chalk, Animal Crackers, Paintballs and eggs ! My local dollar store tosses there old - about to expire eggs and I ask the manager to call me if he has a few dozen - before they end up in the dumpster ...
Very fun and totally biodegradable !