In my opinion if they are not going to get a lot of wear then you do not need to seal.
If mild wear then use a spray sealer like krylon polyurethane. (really LIGHT coat at first so colors do not run) Heavy wear, I would use envirotext light. (This is what the box looks like
http://www.save-on-crafts.com/enlikit8o8ys.html, get it at michaels with a coupon tho)
For necklaces I use bails from after midnight stamps here:
https://www.amstamps.com/shoppingcar...=JEWELRY_BAILS
sometimes you can find good prices for these on e-bay.
to adhere things to it, I always use E-6000.
Yep, you can emboss on them. Watch your fingers tho. They get pretty toasty.
Have fun.
Blessings,
Pam in IN