I don't know about others, and I'm not sure how interactive you'd like your game, but I've had a lot of fun playing and running games on the play-by-post site Story Crafter (
http://www.storycrafter.com).
It has a built in dice roller, as the game master you can set up "acts" that are private so that you can tell individual players things that you might not want the whole party to know about (just yet) and they do allow you to link to images that are offsite (as well as upload "avatars" for your character and whatnot).
It's pretty system agnostic, and uses a message board interface, but if you have players in different time zones or on different schedules, it allows for everyone to easily see where things are then post something appropriate.
Yes, it does tend to involve a lot of writing, but if your games were already more role-play intensive that's just a switch from spoken to "written"
And you can mark the various bits of your game either open to the public (so others can watch your game, if you want) or completely private, so that the game is just for you and your players. All in all, I've found it to be a great outlet for my desire to game (we play a couple of times a month, face to face, but it's just not enough for my voracious appetite
) as well as my desire to just write, write, write (as if this message wasn't indiciation enough of how I tend to just ramble on at the fingertips
)
