Another interesting application can be producing images with higher resolution, or neural image enhancement, like the following figures show.
These figures show more realistic versions of image colorization by Richard Zhang:
Figure 15: Colorful image colorization by Richard Zhang, Phillip Isola, and Alexei A. Efros
This figure shows another application of autoencoders to make image enhancements:
Figure 16: Neural enhancement by Alexjc (https://github.com/alexjc/neural-enhance)