They use AlexNet, which is way out of date at this point and I believe understood to be parameter inefficient. Most of those model parameters are likely useless, and at least less useful than those of other newer models. The model they chose is basically zero-padded and they are appending to the zero-d region.

Also, the newest JPEG standard is nearly Turing complete, so you can possibly compress the data into a program which is the same size as the Kolmogorov complexity of the data.