I prefer to upload to a free hosting site (I use Photobucket) and link from there so the pictures are immediately viewable and not thumbnails, but thumbnails work too.
Martin, I'm sure that you'll agree with
Ras and me, that the good thing about attachments ("thumbnails") is that only members of Playmofriends can see the images.
Also, for our members that don't have really super fast broadband connections, large (or many) images (from a "photo bucket" or "image shack") can take forever to load.
Even with a fast connection, there have been times that I didn't wait for all of Karim's great Victorian images to load!
My two cents worth ...

Richard