I know this question is going to sound really dumb and I do not know. But if you have a high lvl weapon like it's 10 or 100 levels higher than your character, could you use it for just the appearance?
Sure, there's a tab in your character window called "wardrobe" ....just add the item there and you can use it as appearance. Be warned though, the item will be bound there, you lose the ability to wear it for stats later on. Also some, not many, items cannot be used in wardrobe. Wardrobe is really nice, lets you use most any level or class of gear as appearance.
The appearance tab is an older mechanic. The newer wardrobe has the same function, except you can have a lot of items as appearance pieces.
To add what Raff said, putting items in the wardrobe destroys the item, so only put things in there that you want to be permanently attached to the character for appearance only. No clicky effects will work from there and you can not retrieve the items to move to another character or actually wear for stats. But the wardrobe does allow you to equip items for appearance that you would not normally be able to equip at all.
Is it true that Wardrobe feature is only useable by paid members? I'm paying now, but if go to free to play in future don't want lose looks
Everyone gets access to the feature, free or subscriber as long as they have access to the expansion that introduced it (Kunark Ascending I believe) The number of rows you gets depends on how many extras you've bought.