I pretty much use what you’ve got there and just wait for the browsers to catch up. Except, one of the browsers (FF or Saffy I forget) can’t use just any px amount for the degrees. Someone was limited to increments of 15 or only certain numbers at all. I forget who and always use the same numbers : )
You cannot use border radius at all for anything that MUST have rounded corners. It’s just an “extra” for people using certain browsers, and since the -mox and -webkit prefixes are actually used for testing while vendors are working on a property, don’t be surprised if one day a new FF or Saffy comes out and no longer work the same with that code.
border: 1px solid #fff;
-moz-border-radius: 20px;
-webkit-border-radius: 15px;
border-radius: 15px;
There is an actual border radius that you could always set after your vendor code. It will be invalid because the validator only looks at css2.1 and under. Whenever browsers begin to support this property it will be “border-radius” itself.
Padding itself shouldn’t be a problem to using images. Maybe post your situation and code.