Tell me if you really need to upscale your posters I'll add an extra option for this.
Yes, I really need it. I realize it's probably not an issue when the program runs in a window that is not maximized, and posters are of a reasonable size. But I use my "theatre view" skin exclusively, where the posters are in a 450 pixel wide column and the window is maximized. I try to get posters that size or larger, but it seems there are still many that are smaller.
In case you're wondering... I'd don't tolerate posters that are so small they look like crap when upscaled. So nothing is upscaled by more than 50%, and in most cases those look okay. Other users who don't go to the trouble to replace low resolution posters are probably going to prefer the way you've done it.
BTW, as has been discussed before, it would be nice if the image dimensions and size were recorded in the database. That, among other things, would be useful for finding images in need of replacement.