That's a good question! Arms are a big issue for me because I have long ones and because for a long time I danced with crazy arms and didn't realize it (nobody told me how psycho I looked!). I therefore had to retrain them to move with more intention and strength. I can't think of any DVDs other than RBs that specifically deal with arms. But honestly, I think a really big help for me was going back to ATS basics. When you practice at home try to just hold your arms in a high, strong 2nd or 5th postition like an ATS dancer so that you start to develop muscle memory that keeps your elbows lifted up. Then when you start to bring your elbows in towards your rib cage, try to do it at strategic moments when your arms will frame whatever you're doing with your torso (like chest work).
Also, look beyond belly dance for cool things to do with your arms. I'm personally a big fan of jazz dance and foundd that doing some jazz training was helpful for my arm position ideas. But inspiration can be found in all dance forms!
And then also, pay attention to how other dancers hold their arms to get more ideas. I love what Zafira do with their arms. I find their dancing endlessly inspriing---

www.youtube.com/watch

(They really start to do cool things with their arms at about 2:31)

Ariellah's DVD is also great for your arms!