facebook like – image display and description

Use my plugin – http://wordpress.org/extend/plugins/facebook-like-thumbnail/ or the code manually in your functions.php that I have here on my post with explanation – http://blog.ashfame.com/2011/02/wordpress-plugin-fix-facebook-like-thumbnail/

Edit: It will use the first image of your post. Also Facebook will refresh all of your pages in max 24hours, so if you need to force refresh a page manually, try the linter tool – https://developers.facebook.com/tools/lint/

Edit: Regarding the description, if you have a meta named description which you should, because that way you can tell search engines the description of the current page, Facebook will pick that up. Its good both ways, as this is the text people will see below title both on search engines, and on Facebook.