I would get it on the basis of the art rather than the fact that you love RS.
Yes, it's a sweet picture, but, make sure you're not getting it because you love the game.
Personally, I wouldn't have "Runescape" or "RS" included in the tat, but, that's just me.
Unless you get "RS" added artistically. Have it engraved into a cliff or dragon or a cloud or something like that. Make it less obvious then having it bluntly say "RS" at the bottom.
Would you mind posting a pic of the rest of your sleeve? I'm considering getting a one or more. Interested in ideas etc, but not going to get a tat of a game, that's just my preference though.