[black & whites pics from internet and gradiant/transparency]

I have gotten a couple images that are of older people and they are in black and white. I copied them from the internet and my question is How do I or Can I take those pictures and and use the gradiant tool to make them transparent? I have tired and it didn't work, not sure if I am doing something wrong!

[Newbie needs some help merging images for a T-Shirt]

Hey everyone as you know I am new to paint.net and trying to get familiar with it. I hope someone here can help. I am attempting to have a t-shirt made for me with various pictures of people on the front. How do I make it where the edges of the pictures are not so visible on the shirt (which would be grey)? Also does anyone know where to find some really cool images for free that I could use in making some t-shirt? Thanks!!