Watermarking is super simple - as simple as just adding any text over your photos. I use Photoscape, it's a simple, user-friendly, free photo editer & you can add translucent text over photos so it doesn't take away from your item, but it is marked as yours. The best part is you can mark an entire folder worth's of pictures all at once. Here's a link if you want to look into it: http://www.photoscape.org/ps/main/index.php
I attached two examples, the first is a little more obtrusive to the object, the second doesn't cover the picture as much, but it would be easier to crop out. HTH's some!