Podcast show notes - Are there any limitations to what I put in there?

I'm used to including text and links in my show notes, but I'd like to expand it a bit more and include images, some code for layout maybe (CSS even?).

But I'm conscious that different podcast clients may interpret these differently, or even not show them at all so I'm cautious about depending on them too much. Has anybody any experience with leaving detailed show notes and changing the formatting a bit?