Thumbnails for posts as gallery

Hey.
I’m making my new portfolio with wordpress, and I’m looking for a plugin that takes a thumbnail i assign to a post, and place it in a grid gallery without any text or anything, but with a link back to the post. I’ve tried the Post Thumb plugin, but it’s made to generate the thumbnails using images embedded in the posts. I need to be able to make the thumbnail myself, and then assign it to the post, so it automatically updates in the gallery.
The reason i don’t want to embed any pictures, is that I’m using a flash slideshow inside each post to show off my work.

I hope you guys can help me, I’ve been trying to do this for weeks, and it just keeps getting more and more frustrating.

//Nithel