Images used in Arrowchat should be optimized using something similar to
https://kraken.io/ (Lossless Compression) to reduce unnecessary, and often wasted downloading of larger uncompressed images. I had to do it manually but I was able to shave a rather large percentage off the images which speeds up loading time for the end user as well as saves a couple of KB to an MB of Bandwidth (which if you have lots of users, adds up).