Here is a technique for you to try.
You will need:
Judikins Diamond Glaze
Fill the watch crystal with the Diamond Glaze, but leave room for the watch innards. Choose the watch innard pieces that you would like to use for your project. Place your pieces on top of the Diamond Glaze, and carefully sink them in the glaze using the toothpick. Refill with more glaze until it is flush with the top edge of the watch crystal. Let it dry about 1 hour. I cut a watch image out and placed it under that dry crystal before gluing it to my ATC. There you have it. You can also try other small objects or charms, some glitter too perhaps. Or use a face image, or anything under your completed epoxy embellishment that will match your ATC theme.