Images not stored in Databases

Hiya, I have had help from a very useful person on storing images in databases, and basically now I don't want to do this. But I may end up storing a lot of pictures, and don't want to mess around. Is there a script or class, that is as simple as storing in a database, that will handle possibly millions of pictures, and given a picture will return the URL where it is stored? I suppose I could build one myself, but I can see it being quite difficult, with problems such as maximum number of files in directories etc. I have had a look at a few PHP pages, but cannot find anything suitable. Any help would be great. Have a great Christmas. Love, Steve XX