I think the problem may be that you're only setting one background size, which gets applied to both background images. If you change it to something like:
background-size: 125px 125px, 100% 100%;
you might get the effect you wanted. Without seeing the applicable HTML, it's hard to test your code.
It would also be a good idea to add multiple instances of your 'background' rule to include the other vendor prefixed variations of linear-gradient, as well as the standard. Webkit browsers dominate, but they aren't the only mobile browsers out there.