Image table is getting really big (T222224#6738823) and it turned out ~90% of the space taken by image table is text tag in metadata of pdf/djvu files (T28741#6750249). This needs addressing as it's causing infrastructure issues.
One way to do it can be to compress it, the other can be to push it to another storage like another table. the third way would be to delete it and read it directly from the file if needed. See T28741#6750249 onwards for more discussion.