i dont think its a good idea to save pictures (for a gallery?) in the db, for obvious reasons (just think about performance)
in my gallery implementation i used acts_as_file_column (i think that was the name), but that plugin is not developed anymore, acts_as_attachment shall replace it. these plugins save the file on the disk and use a column in the model to store the filename in (or some other technique).
this way you can even integrate RMagick or some other sort of processing, creating multiple thumbnails in various sizes and stuff.
so my tip is: dont use blobs to store “attachments”