I like celosia for flames - my DH is a fireman and I often plant these around our mailbox. They also come in orange and yellow, so it's fun to mix them to get a "flame" look if you stretch your imagination.

Here is a link that might be useful: Celosia

I agree to the celosia. I have a fake fireplace that I did that with. They like it hot and can stand a little drier as most potted plants seem to dry up quick.HAVE fun.
tanya

I think the celosia would be terrific too. If you want something low and draping, you can never go wrong with petunias for a lasting color. I say mix them all up (its what we do best) hahahaha

Oh! I love the idea of celosia! It's one of those unusual looking plants and with mixing colors, I could definitely "see" fire! Thanks for the suggestion!

Astilbes might look nice. They make good cut dried flowers too.

Here is a link that might be useful: Astilbe