In case if you are bored, here is another extension suggestion. An extension developer can make style transfer extensions that style transfer two images into one.
For example, a user takes an image of the Macau Tower.
Then, they select a drawing by Vincent van Gogh.
At last, the app generates a van Gogh styled Macau Tower.
For more details, visit here.
https://dzone.com/articles/java-art-generation-with-neural-style-transfer
It would be a difficult project though.