There are currently 2 somewhat irritating issues with item preview:
1. Whenever you preview something while wearing an outfit, the headgear of the outfit will also be displayed, even when you have it turned off. (When not wearing an outfit, your head gear will not be shown in preview, so it must have something to do with outfits specifically). This can be annoying and I could not find a way to work around it so far.
2. Previewed weapons will always appear in “human size”, so e.g. they will looks overly large on an Asura. You can work around that by swapping weapons, but it would still be nice if that was fixed. The same thing also happens when you open your hero panel and it also happens with back items.