Unfortunately not all items appear in the wardrobe tab though the vast majority do. For the rest you can search the wiki then copy-paste the chat-code ingame to preview them. Places like https://wiki.guildwars2.com/wiki/Gallery_of_pistols can be a good resource. As an aside, I find the pistol skins to be some of the worst in the game. Maybe it's just because they're small, but I find very few of them visually interesting. If they fit your theme, alchemical, glacial or nightwing are pretty good, while the X legion ones are decent as a generic option. Qadim's is great but obviously hard to get.