It starts very simple: Find a picture. This one will work!
Next, take out the messy background. Let's put our soon-to-be-Gordon in City 17. That light in the background matches the light on the Gordon!
For this Gordon, I burned his chin to make the goatee, copy+pasted some nerd glasses on, then drew frames around them to match Gordon's iconic glasses, and found a picture of a crowbar on the internet. Color replacement fixed that blue crowbar right up!
No Gordon is complete without the Lambda symbol, though. I didn't feel like copy+pasting a whole HEV suit onto this guy, so I drew one and burned it up a bit!
Now, you have your very own Half-Life 4 Gordon Freeman! This is the one where he doesn't have an HEV suit, and instead runs around in jeans and a wifebeater. That's just how badass he is, now. *nod*