It's possible to create a custom avatar?

Hi,I've been tinkering with the PS3 quite a bit and found a way to install tons of custom avatars in edat format,I wonder if there's a way to download a random image from the internet and convert it to edat and install a custom avatar that way (that shows on PS4 and vita too).

Is this possible? I've seen some videos suggesting that is possible but I would like to know how.