It depends on the resolution of the original image and how big you want to make the image. A low resolution image say 100 x 100 or less will not look very good when printed at a 11" x 15" size.
If you find something and want to know how it will look at a certain size just let me know. I can blow it up for you and send it back to you so you can see if you like it or not. No charge.
It's also worth mentioning that flaws due to low res will become more noticeable when printed than when viewed on a monitor. Let me know if there is anything I can do to help.