ομφαλός (belly button) is quite weird for ο (omikron), but I can't think of something better!

Just listing the letters below and my rating for each letter, maybe someone has a better idea for some of them:

α - αχλάδι (pear) 5/5

β - βάρκα (boat) 5/5

γ - γίδα (goat) 4/5

δ - δεινόσαυρος (dinosaur) 4/5

ε - έντομο (insect, bug) 4/5

ζ - ζώνη (belt) 3/5

η - ηλιοτρόπιο (sunflower) 3/5

θ - θρόνος (throne) 4/5

ι - ιππόκαμπος (seahorse) 3/5

κ - κάκτος (cactus) 2/5

λ - λιοντάρι (lion) 4/5

μ - μάσκα (mask) 4/5

ν - νυχτερίδα (bat) 4/5

ξ - ξύλο (wood, stick of wood) 2/5

ο - ομφαλός (belly button) 1/5

π - πόρτα (door) 4/5

ρ - ρακέτα (racket) 4/5

σ - σαλιγκάρι (snail) 5/5

τ - τραπέζι (table) 5/5

υ - υποβρύχιο (submarine) 4/5

φ - φίδι (snake) 5/5

χ - χιόνι (snow) 2/5

ψ - ψάρεμα (fishing) 3/5

ω - ωκεανός (ocean) 5/5

I'm basing my rating on how common a word is, and how much the shape resembles the drawing and vice versa.