Light-bulbs are one way of doing it - as seen on the cover of my memetics book or in Pat Linse's now well-known illustration for Susan Blackmore's The Power of the Meme Meme article.
Another approach I came across recently was in a paper titled "Memes and Fitness Landscapes". It is shown to the right. I tracked down the original. It is an illustration by Adam McCauley created for the article The Meme Hunter - by Andrew Brown.
Somehow the hairy legs and red gloves/boots remind me of a housefly with dirty feet.
I rather like - but meme critics will probably hate - this kind of "agentification" of the "meme" meme.
Part of my interest in the theme is as possible inspiration for the cover of my proposed "memes" book.