You could work at Macca's if you wanted let alone another job category - DIAC doesn't really care what happens after you move here. As others have said, you could even open your own business.
The only work restriction is on federal government (Commonwealth) jobs, which are generally open to citizens only.
In the end, I ended up working in a different role from the one I had initially nominated (although it is related). It worked out better for me because I realised pretty quickly that I didn't want to work in my original role anymore! (At least not here.) And no, I don't work in IT.