There may be a simpler way of doing it, but what I did took some thought and tinkering. I copied a picture - the symbol for iHerp - to my photobucket then inserted that into my signature just like you would for any picture. I then highlighted the picture link and clicked the button to insert a link and used the iHerp link to my page.
It really wasn't difficult, it just took a little trial and error to get it to work. But if there's an easier way, I'd be interested to know.
And I don't know how you get the long, narrow bars for iHerp or other links/ads for your signature, so I'd be interested in knowing that too!
I'm no computer guru, but hope this helps someone. If some of that didn't make sense, ask away and I'll try to explain better.....