Mysql has a limit of 1Mb for storage.
You can change it my modifing the my.cnf file. Personally if your on this step I would move to filesystem storage. Large objects in the db could lead to speed issues and stability problems, but thats a personal view. I _always_ set to file system for both image and file galleries
p.s. there are other recent posts with details of what to change in my.cnf