Theme viewer like plugin

This doesn’t require a plugin, unless you’ve got something more complex in mind than what you said. But from what I understand you’re trying to do:

Just upload a small picture (in a post), and link that picture to another page. Done.

Thats pretty much what I want, I have a free template site, and I would like to post them in that format

I believe Adamrbrown is suggesting you just use the built in image uploiad function and select the thumbnail option and link to image.

That would be a quick and dirty way of doing it, but you may want to look at any of the image gallery plugins available (Nextgen, AWSOM Pixgallery, etc.) and see if any of them work the way you want. In that case you have more flexibility if you need to re-sort the images or break them up into multiple pages of images.