Various expressions we've seen on Spike:

He looks pretty scared here... ...and here... ...and especially here!

Let's not forget about here...

Waking from a nightmare
Watching Faye's tape. Heart is all over his face

Spike with the blind Stella. Look at that face!

Hungry, tired and unhappy (Mushroom Samba) Has something dangerous (fun) to do. :D
Sharing a sad laugh with Jet Silly/goofy Fond smile at good memories

Perplexed or frustrated?

Oh shit. Don't wanna but I gotta.

Regret?
Bored? Vaguely interested? Hung over Nothing special, I just love this pic


Here is a whole section devoted to a pissed off Spike:

"I'm gonna salt you and eat you!" (to Ein) Just tuned up guys who thought he was Vicious Seeing Faye in a Scratch promo. Disgusted, no?

Shot in the arm. Pretty pissed - The BEAST

Shin dies - grief and rage - The BEAST Finding Vicious. Hate and rage. OMG - The BEAST

These weren't in the show, but from "Cowboy Bebop Illustrations - The Wind" by Toshihiro Kawamoto.  I have to include them because in the course of the show, Jet and Spike didn't really have anything to laugh about.

The captions he provides are different, but they have 2 things in common. They both say "the two guys laughing like idiots" and "before they encountered Faye."  I love that Spike is hanging on Jet in both.  These are my absolute favorite drawings in the whole book. That's saying a lot!

 

Spike, how he must have looked when he and Jet first met (roughly, but maybe wearing the same clothes we're used to seeing him in)

This is how I picture Spike when he first met Jet in "Io Tango."

The three after Vicious finds out about Spike and Julia.