upon further investigation it's considered bad practice to use gzip for binary files or web images in general. using gzip can INCREASE the file size. check this
> Image and PDF files should not be gzipped because they are already compressed. Trying to gzip them not only wastes CPU but can potentially increase file sizes.
You could use something as trimage to optimize your JPEG.
My post wasn't totally clear : optimize means losslessly compress the jpg files. I know 3 free apps for this :
Caesium for Windows : http://saerasoft.com/caesium/
Trimage for Linux http://trimage.org/
Imageoptim for Mac https://imageoptim.com/
As far as I know, Photoshop is not the right tool for easy batch compression.
You could add optipng to the Bitmap Compression list. You might want to consider adding "lossy", "lossless", and "both" classifications for the entries (if possible) since comparing the two is like comparing apples and oranges. At least the first one on the list, TinyPNG, does lossy compression instead of lossless. Oftentimes if you're using PNG you actually want lossless files, for lossy there's always JPEG.
Which reminds me, you could add a JPEG optimizer section as well. I only discovered lossless optimization of existing JPEGs a while ago and I find it fascinating. The only tools I know of are jpegoptim and Trimage, but I'm sure there are others.