My publisher had posters made of my book cover, and they are amazing. I liked the variety of sizes they came in. The quality of the paper is great! I have one on my cube at work, and soon I'll have one framed in my apartment. I plan to order more to bring with me to signings. The small and medium posters are pretty big, so I definitely wouldn't want anything bigger than that.
About the print:
The printing was amazing. The site warned that getting larger posters than recommended would distort the image quality, but I got a small and medium sized one, and the picture was great!