I realize that the viewpoint is from above, but the cup Miku is holding can only be described as a bloody cereal bowl because of it's size in proportion to her head (from an downward viewpoint her head would be closer than her cup which is at or just under the nipples of her breasts), heck she could fit one of her breasts into that cup and still have room to spare.

I've seen "cups" like that before. My dad use to have something similar. Hard to say if you would call it a "big" cup or a "bowl with a handle" though. I used to think of them as a big soup cup.

On the other hand, its could be simply wide and shallow. Also, the perspective actually looks more like the cup was meant to be closer to her neck height. Of course, that's not really possible considering her arm positioning. JPN artists aren't very well known for technical accuracy like proper proportions at times. (Just look at her fingers, especially the index finger...)

A lot of coffee chains offer mugs that size here in the UK:

http://lh4.ggpht.com/-2VQzsi_LQqw/T_rwK2f6vQI/AAAAAAAABfU/0Sd59O7mFsM/Rome%252520and%252520London%2525202012%252520457%25255B9%25255D.jpg

Also keeping in mind that Miku is a small female, so the mug will look even bigger in relation to her