WordPress.org

Is not working for me. Why?

First, the question is too generic. But the main cause may be that you... don't use excerpts! If your theme do not use the_excerpt() is obviously that this plugin will not work. This is Thumnails for Excerpts. I repeat: Excerpts!

The thumbnails are present in feed?

Yes, if you don't provide full feed, than this plugin will put thumbnails to excerpts from your posts.

Can I choose the size of the thumbnail?

Yes, open the PHP file and see in the top of it.

Can I choose the alignment of the thumbnail?

Yes, open the PHP file and see in the top of it.

Can I further customize the look of the the thumbnail?

Yes, with CSS. The thumbnails are usign imgtfe as default class, but you can change it.