You mean that big 1024x1024 one (that looks best if done at ~3000x3000 and resized)? I need to make one too (and that a reason why I can't help you with it, at least now). Or about animated one?
I want to ask actually, did you consider to change his appearence a bit (that ate a lot of extra time by dull copy/paste elements one by one before editing them, yeah, but make him distinct from common couriers, and it's a area where I can help a bit more than with big one)?

About big pic (in case when you didn't read my comment at Klei forum), gui.kwad contain great 3172x3172 pictures for archived Prism and archive Sharp that can be a good starting point to see how Cheoljoo Lee create them. While start with 1024x1024 in Photoshop/Gimp can lead to some pixels/blurs problems (vector graphics from Adobe Illustrator could be the best option, but I'm not familiar with it and didn't tried it).

That's interesting, I didn't find the 3000 x 3000 ones. I did a pretty hack job on mine with the 1024 one. I could modify the appearance slightly, but I'm feeling fairly confident that I know how to mess with the animation.
I'll dig into it, but if anyone has time and has any talent I'd be happy for some help. The 3000 X 3000 is where I'll start, though.

Messing with animation is quite easy: anim file (like those in API example) is a zip archive with two xml files (that can stay in peace) and a bunch of png sprites that can be edited and packed back to anim archive. Problem is only that KWADTool slice sprites from sprite-sheets without supposed empty spaces around and to recreate any character it require to manually put every sprite over Decker's one (or over Banks).
Animated portraits a bit trickier: example mod contain portrait .anim build of guard so there's a standart guard's proportions (those can easily be conquered by xml edits), not much of a movement, eyeballs are paired (that's a big problem: portrait design need to be build around constant space between eyes),

Strelock keep updating KWADTool: v1.1.0 Alpha extract png sprites/symbols with their invisible alpha spaces around. At least when you use command like "KWADTool -i your.kwad -e Anims -o yourDir"
https://github.com/Psimage/KWADTool/releases/tag/v1.1.0-alpha
So now if you want to combine or edit some character's appearence you don't have to manually put sprites over Decker's or Banks sprite but simply combine extracted pngs!
Character's visual modding should be 50-75% easier now!

Well, that I have translated the guide I think I can give this a better shot now. Standby as I mess with it.