Thumbnail issues

Hi, my first post here, so apologies if it's in the wrong place.

I've just switched my xbmc skin to MediaStream as i think it looks amazing.

Unfortunately mine looks rubbish!!

I use xbmc to stream videos from my PC, it's set up as a network location on there, when i open the folder, navigate to 'tv shows' or 'films' it just says 'no thumbnails', it does this all the way until i get to the actual video file, then it shows that as a thumbnail.

Looking at the gallery on this site they look amazing, not sure what i have to do though.

I have tried putting an image in the same folder, so for example within the 'shows' folder i have a folder called 'American Dad' and an image renamed to 'American Dad.tbn', thinking then that when i navigate to 'shows' the thumbnail should show up, but it doesn't?

Also i see some people with a film sysnopsis up, that must be automatic right? How does that happen?

Sorry if none of that makes sense, or if it's a ridiculously obvious thing, but for the life of me i can't work it out!!

Thanks in advance