Now in Google Images in the Tools tab, then Sizes you have a list of Megapixel filters from Advanced Search.
The options are:
Larger than 2 MP Larger than 4 MP Larger than 6 MP Larger than 8 MP Larger than 10 MP Larger than 12 MP Larger than 15 MP Larger than 20 MP Larger than 40 MP Larger than 70 MP
If you want to contribute to the extension, feel free!
