It depends on the capability of your system. Until this week, I was running a database this size on an eight year old machine. Many operations were very slow, but it worked. As for the size of screenshots and other images, I doubt there's any reason to be concerned. Regardless of their number and size, managing them within the database is less error prone and more efficient than leaving them out in the file system.
As for the number of movies, there's probably reason to be concerned—but not the reason you may think. My database has 1,700 visible movies, ...and 220,000 "invisible" movies. There are this many because it's saving records for the filmographies of the 28,000 people in the database. This is a lot of people, but (theoretically) they're just the ones associated with the visible movies in the database. The number would be much higher if I did not use the option to restrict actors to those included on the IMDb main page (the top 15 credited).