Loki, being a favorite subject of mine of course, prompted me to pull together all the info I've known about for sometime into one post. So that's what follows for anyone who may be interested. I'm preserving the info for posterity because I'm lazy, and I like being able to call up items by my tags. :)
There's not a great deal of Loki merchandise around, why? Well simply put there's not alot of known depictions of Him from pre-Christian antiquity. Most of the statues that are made for the Norse Gods are based off of archaeological finds.
Most merchandise I've seen is based on the Snaptun Stone, such as a Loki plaque, and a chocolate Loki you can eat. I’ve seen a pendant variation as well.
There’s also another Loki pendant based off of a find in the British isles, where he's bound hand and foot.
Additional appearances in antiquity include the Kirby Stephen Stone, and the Gosforth Cross (which depicts Loki bound with Sigyn holding the bowl to keep the venom away), and was the inspiration for this work by Collingwood. I include this second piece because 1) it depicts Sigyn and She doesn’t get enough attention, and 2) I think it helps make the depiction on the Gosforth Cross a bit easier to understand.
I've also personally wondered if perhaps the Aarhus Stone may be a depiction of Him as well, something about the design of it evokes some of the motifs seen in other stones mentioned above, and reminds me of a goat (and thus the story of Skadhi's laughter). But the depiction does seem to have some elements similar to what's been identified as Thor elsewhere. In the end the depiction on the Aarhus stone remains unknown.
Beware though, lots of people mistake this pendant (from the Varby Hoard (Swedish), from about 940 AD) as representing Loki, however it represents Utgard-Loki, leader of the frost giants. And since there’s a story where the two appear at the same time, and one's frosty and the other is fiery... the end result is that Utgard-Loki does not equal Loki. Another version of this is depicted here, which leads me to believe that this other version (the pendant you guys have posted previously) is in fact yet another deriviation from the same archaelogical find for Utgard Loki. If you compare all 3 of them, it looks like a progression in design of the same image.
I was gifted with the last bracelet (based on an archaelogical find in Denmark) on the page here, as it reminded someone of Jormugandr, and thus Loki.
I personally have adopted the symbol of a “Fish” to go with Him. Why? Well, He can be slippery like one, it embodies his ability to be more than ordinary, and obviously it’s a reference to the Lokasenna. I’ve created necklaces along this line for me and a fellow Lokean. Also, the image used on my avatar is an artpiece that just for some reason reminds me of Him. It's from Caspar David Friedrich's, "The Wanderer Above the Sea of Clouds".
For new art, Deviant Art has a few illustrations, and some of the prints are even for sale so you can order them. Most are handily linked from this Loki themed club on the site: http://lokiclub.deviantart.com/
Here are some of my select favorites: