http://www.gimp.org/

I imagine you're thinking of text overlays, in which case you need something like Gimp (although I'm not sure it even has a text tool) and some fun downloaded fonts.

http://www.1001freefonts.com/

HOWEVER, as a regular GM I still do not approve of people going out to the world of Facebook or the wider internet to pull down pictures of generically handsome people to use as a face-claim for their character. Not only is it lazy from a written perspective to make that image publicly known to be your character without any attempt at describing him or her in-app or in-character narration, but there's also a certain legality question to it. As a photographer too, I would be annoyed if someone went and used a picture I took of someone I was asked to do - or I asked them if I could do - under certain controlled pretenses.

Role-players are not in my pretenses.

There's also a lot of legal and ethical gray around minors that gets even more scary the further you go back. So just don't do it, please don't.

If you have to have an image then I'm sure you can find a free artist out there who will try to do something with the written description just to have the basic recognition of someone wanting something for them. DeviantArt is littered with amateur animus who will be all too happy to make your faceclaim for you.