Welcome to our community, TechDocGreg
I use images all the time. I've never known them to break my
help system. And I used to have a TON of them. (I documented lots
of hardware - think gobs and gobs of photographic images of
assorted hardware in different "poses").
Sure, images will likely cause the overall size of the help
system to swell, but that should be a big issue.
Nowadays I tend to exclusively use .PNG format for all my
images.
If you have a need to make a topic appear to be slim, you can
tuck the images inside Dynamic HTML (DHTML) drop-down hotspots.
That way they won't be seen unless your user really wants to see
them.
Cheers... Rick