Hi Everyone,
I am currently modelling a (relatively) low-poly cartoony cat. I have just about finished the head and added two different materials to it (it is all one mesh, excluding eyes/nose) however have run into the problem of giving the model a mouth. I’ve decided that to tackle the issue I will UV unwrap an alpha texture of a stereotypical cats’ smile which I have generated myself.
I was therefore wondering if anyone knows how I can add this image texture to a mesh of multiple materials. Below is a screenshot of my current blender window (messy I know ;))
At the top left is where the mouth will be (below the pink nose) and on the top right is the alpha image texture that I want to add 
Ok having problems attaching the image :L Anyone with any ideas how to attach the photo as well could u also post below, sorry i know im being super Nooby! 
Haha thanks, eppo! ;D For some reason I cant attach files via the attach file icon in the reply box? :S Anyhow, here’s a link http://www.pasteall.org/pic/48317 http://www.pasteall.org/pic/show.php?id=48317
Ah… Cycles. Might be so then.
Images could be inserted via second to the right from envelope icon. Attachments are available when in Advanced mode (big orange thing below the text box; look for clippie then in toolbar)
Ah yes sorry, forgot to mention it was cycles ;D Thanks so much, eppo, you’ve been a great help and your method worked perfectly!
Here’s a current screenshot 
http://www.pasteall.org/pic/show.php?id=48399
http://www.pasteall.org/pic/48399
Thanks again ;D