There are actually quite a few write ups here in the Monastery regarding images and DBs, however the general rule is to put the pointer in the database (or path to the image if you will), and store the image in a directory in the filesystem. That way you reduce the load on your database server and it *should* keep things speedy.

This node covers a pretty great deal of information involving images and databases (and even breaking up large images into chunks to keep download times sane).

HTH