Enlarging Thumbnails

There are a number of thumbnails that I downloaded for the purpose of displaying in both Movie Collector and XMBC for visual ID of movies. Most of these work fine, but too many become so blurry when enlarged, that they become useless. I think that this is because the source image is so small that they just won't enlarge properly.

I do know how to enlarge graphics in a number of programs designed for the task, but as far as I'm aware of, that would be subject to the same limitations that are found when enlarged by the two programs mentioned. Is there any way possible to retain the same detail in an enlargement, as it started out with?

I have tried to find bigger images to work with, but when dealing with really old movies, one must take what one finds, and I had to look pretty hard for some of the images that I did find, which are not working out.

i'm afraid it's impossible to add detail when enlarging - there is always going to be quality loss, as the software has to guess the colours of the newly added pixels; and, as we all know, computers are pretty dumb. :)

amazon and other online shops might be a good place to find better images for movie covers - or have you looked at imdb?

Yes, I have looked in those places, and many others. Like I said, most of the time I find something suitable, but there are cases when that is not so. When you go back to some of the really old movies, which were never released on DVD, the pickings can get very scanty. The only alternative that I can think of, is to make my own thumbnails, but with my very limited talent in that direction, I don't find the thought very appealing.