For Gaia there is Tektek, the place we use to preview items on avatars and make up avatars.

There is also Market place good for previewing.
But on here, is there anywhere i can go to get previews of items not in the shops?

There is :) You can try it our and post some feedback about the beta over here http://www.menewsha.com/forum/main/dream-avatar-beta/

Whenever I click that link, it won't work for myself, and I know that someone else can't go to it as well, this is what I get when I click that link:

misfittbaby, you do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

The dream avatar thing is still in beta you can only access it if you've previously donated to the site I believe.