Ship nextgen image formats

I love CalTopo, but sometimes get frustrated by its sluggishness. When I'm in the field doing survey work I usually have already downloaded the maps I need, but there are plenty of times when I don't have them saved and loading is slow or refreshing is hindered.

Not sure how extensive and painful it would be to implement, but moving away from PNG as the default image would really help in this regard.

For example, here's a typical mobile experience:

Here's one tile I pulled and just converted with no real loss in quality and it's a quarter the size.