Great script, very useful.

But why pollute your scripts menu, when we can do this context-sensitive?

Put the scripts in a local place, like ~/bin or ~/scripts or wherever you like. Select an iso, choose properties, and look at the Open With.. tab.
Click add, click 'use custom command' and click browse. Select your Mount script, then repeat this with your Unmount script. Now you have in your context menu whenever you select .iso files, an option to mount or unmount!