For CS/OOC/IC they are great if it is just a banner picture of something but anything beyond that seems to bother people. I did a RP that was based in Britain and decided to have the text for the idea to be red, blue and white because of the Union Jack flag. I thought it looked nicer but other people were put off it, it was only one little part of the text. I did a "The army needs you" type of thing, like those posters we have but they seem to be rare now. The one with the guy pointing at you as he says those words. A banner makes a dull place less dull. I do sometimes do it for speech texts when too many people are RPing at one time. I also do it to convey tone, I set out what colour means what so the reader understands but it is rare I do it. 

Bold and Underline add to a thread looking less boring, even the Italic does the job. I like to make things pretty but I have to remember some of the things people tend not to like. So a banner, some bold and underline and you should be set. I do want to remember how size of the font is done because that adds to it as well.I also like to write chapter names if one part is done.