It isn't the first subject asking to add this feature, but none received any answer and are really olds.
The actual marketplace permit to preview items & clothes only with a picture - and that picture, sometimes, doesn't even show the real article.
It it necessary to permit players to preview clothes, hair & avatar. Clicking the "Preview" button on the marketplace will open the "edit avatar" view (or maybe a new one ?), permitting users to use the native functions to scale & move the preview item, and a button to buy and apply it directly.
What do you think of it ?