Some forums allow the display of full images and others crop the images into thumbnails. Is it a viable option, meaning will it drive people away or entice them to sign up, to have images only be visible when logged in? When logged out a short "please register to view images" type of message would replace images.

SEO benefits to forced registration include faster load times and reduced bandwidth useage from search engines. SEO negatives include missing a chance to have images indexed in search engines on their own.

Another positive to forced registration before being able to view images is more control over who see's what. Members can't hurt your rankings by posting adult material and copyright works don't get spread around the net by search engines.

My main concern however, is seeing a registration request in place of an image going to turn people away in droves or will more sign up? Sometimes people will actually become important members if they take that first step. Also, registration would provide access to other parts of forums usually reserved for members anyway.

What are your thoughts ?