@Rowan-Ferguson Hi Rowan, I quite like your first one because of the texture you've got in the background to pair nicely with the vector elements. The second one is a bit too digital looking IMHO which makes it look more 'generic' since there isn't as much unique about it from other digital artists out there. I think if you add in some of that nice texture feel into your second one it would give it more charm You've got great colour harmony in both and they're strong compositionally too btw
Love the top hat on the lookout bug!
That said - I think you should stay true to your style. Just because classes/critiques talk about a more traditional approach to art, doesn't mean you should conform. I don't know if you're going a comics direction or children's book - but I think either can work with a flat style. Comics in particular are quite flat, but there's a few children's books too that have done really well with a flat style that are just gorgeous I think: check out Grandad's Island or Mr Tiger Goes Wild