I use tinypic.com - you upload it into there and then it gives you various choices inlcludung "IMG Code for Forums & Message Boards". I know there are other ways as well, but I find this pretty easy.
Probably this one as it reminds me of my (non horsey) brother's immortal response to the question, which horse do you prefer?....."The one with the feet-beards!" (aka feathers)
Loads of atmospheric pictures! Love the feet-beards!!! Also the dream team Ester - hard to work out which way those gorgeous little beasties are going. Just remembered this one as well from the ranch we stay at regularly in Montana.