Step 2: Compression
You've saved your horse avatar as a JPG/JPEG? Good.
This should be the only thing you have to compress, but if something else comes up as too big a file size (which I've never seen, but you never know!), these same steps can be followed.
Below is the before and after of a horse avatar I recently made for a player, and compressed:


Can't tell the difference? Good.
The top one is the uncompressed one. I told it to go as high as it could after cutting it into a horse avatar. I saved it as a JPG, it ended up at 290KB. The second one is the compressed one, still JPG, at 83.4KB.
( I will hunt you down if you steal it, so don't :D )
Compress Where? Versa?
I go here (link).
Cut your art into a horse avatar BEFORE uploading it there.
Drag your horse avatar cut into the upload, the website I linked above. It will take you to a new page. Wait for it to finish.
Do NOT choose the quality option!
Select "max file size" above it (notice: it ONLY works for JPGs), and tell it to compress it to 95KB.
Let it load. Download the image. Done.
Your page should look something like this:
