Like his painting of Sulu, Kelly perfectly captures the facial features of Chekov, who actually seems the closest to his 1967 self than any of the others. And oddly enough, whereas most of the others gained longer hair (based as most were on photos of the stars taken at the time, the mid-70's) Pavel's is the same as the series; maybe Freas judged his Monkees haircut shaggy enough already. Nothing added to it for visual interest, as in most of the others, either; a phaser or something would have added a little zing. I would have given it an A+ for character accuracy, but I deduct a bit for the lack of flair here that had been given to the others. But for the very nice starfield background, this would have been somewhat lackluster. Even his expression seems a bit distant and sad; whereas his buddy Sulu looked happy and energetic, Chekov looks lethargic and introspective.
Maybe the expression comes honestly... Chekov always seemed to get the crappy end of the stick; a Ceti eel in his ear put there by Khan, an butt-ugly Drill Thrall who wanted to molest him on Triskelion, a plasma-burned hand when V'Ger overloaded their shields, brain injury on an aircraft carrier in Earth's past, shot and "killed" in the Melkotion OK Corral illusion... even his Mirror universe double fared no better, as he end up screaming for hours in the Agonizer Booth. Chekov was famous for screaming in terror and/or torment; that would dial down your enthusiasm level.
Or, perhaps it was taken from a then-contemprary photo reference of Walter Koenig, who probably was depressed at his lack of work after the series, and was forever ambivilent about his typecasting. His interviews and book "Chekov's Enterprise" all bemoaned the fact that he was so underused. The one convention I saw him in, where he was onstage with TNG actress Marina Sirtis, he looked uncomfortable, as if he had been ill, or eaten lunch at Taco Hell. Though, to be fair, I guess years of people asking him to "say 'nuclear wessals!'" would drain the joy from any man. He could probably relate to "Galaxy Quest" more than any others of the cast.
Bonus: Below, the salute to Walter Koenig from Starlog's Trek 20th Anniversary issue #112.