Edit right click menu style is it possible?

[artrbinfo]

Hello!
I'd like to give some nice background gradient overlay for right click menu, and give round corners to it. Is it possible? Maybe there is some theme what I could just edit?
Thank you!

[artrbinfo]

I found one theme with menu background, but is it possible to round right click menu corners?

[artrbinfo]

I think that there should only add top and button .png to make rounded corners, I have heard about widgets, what works the same as original right click, but what is possible to theme better. Does anyone know something about possibility to round right click menu corners?