You might want to just try it out with some test pages.

Benchmark the differences between serving static images (with the paths determined from information stored in the database) and images straight out of the database.

Besides the performance differences, you also need to consider how to put the images in safely. If I make the assumption that the course materials will be maintained through webforms, you have to remember you will need to deal with getting the content in as well as getting it out.

Some other gotcha's might be not being able to use certain sql calls depending upon the database (older mysql wouldn't allow groupby with blob or text fields for example).

Personally I would give it a test though, it is an interesting exercise, and under the right circumstances a nifty way to handle certain problems. For example, one site I maintain has little images of authors that I keep in the database...they are used on several sites concurrently. Keeping them in the database means I don't have to worry about having common directories, and whenever they add new sites, the author bio section is plug and play easy. I had to compromise and not allow the client to put the images in themselves (to check sizing and for security), but they can handle the rest of the info through a web form.

EEjack