Ben Langhinrichs pointed out that there is some notes.ini magic to solve this.
The magic line:
Explanation on Andre Guirard's blog www-10.lotus.com/ldd/bpmpblog.nsf/dx/purpose (Andre's very first post)
When I paste images into a rich text field, by default, they are pasted as bitmaps. I can choose to paste them as deveice independent bitmaps (via Paste Special)..., which hugely (by an order of magnitude sometimes) redues the size of the pasted image. So why not default to the more space efficient encoding?