As I have mentioned before, Custom items are one of my favorite aspects of SWTOR. Like an appearance tab, they allow you to control the look of your character. What they do better than an appearance tab is keep the items a part of your gameplay instead of setting and forgetting.
Since Custom items are all about looks, it's important to know what look like before you buy them. To do this, just CTRL Left Click on an item and viola, a dressing room window. This can be done on vendors, your inventory and the Auction House. Also, you can check out companion appearances this way too.
Here I am trying on a new helmet, Commando's Helmet, which is cratfable by an Armortech. You can also see what it looks like on your companion. There are no class restrictions in the dressing room either. So try on those Consular Robes if you want. You can rotate the model in this view as well.
Sadly, you cannot seem to see what a weapon looks like in this view. I hope they add that feature soon, as choosing the right looking gun is very important for a fledgling Trooper.