Good start, but they need weathering and proper highlighting no matter what. That's just part of modelling in general.
Highlighting, as its most basic, is fading the colors and making the edges brighter and shinier. It adds definition, and there's multiple techniques for doing it.
The quick way is "dry-brushing". For example, if you wanted to do the edges of your bombs, you'd paint them a darker metal color. Then, with your lighter color, get a bit on the end of your brush, and wipe most of it off on a napkin. Now lightly brush that over the surfaces. The paint will stick the the edges and brighten them up.
Highlighting by hand is very, very time consuming. It involves anywhere from 3 to 102983213 shades between the colors and requires an exceptionally steady hand. For my generic troops in warhammer 40k armies, I tend to do 7 shades, and 15 shades for leaders... but those are for competition and affect tournament point scores. I'm not very good at it
Inking is a "cheater" method imho, but it works. It's literally an ink, so make sure you cut it with water, then simply "wash" it over the model. The ink well settle in crevices, dry, and darken them up nicely. The downside is that sometimes it turns out too shiny (at least for my liking).
Black-lining would really make the colors pop and be a beautiful model, but you lose a bit of the realism. That, imho, is better for personell instead of vehicles, but I've seen it done before.
Weathering just makes stuff look used. I prefer mine in parade ground appearance, but iirc, a good technique is to use wall spackle mixed with brown paint. This gives a nice "mud" you can apply with a brush. Running your thumb over a toothbrush loaded with it can give you some really nice spray patterns.
Try this site. It's actually for miniature wargaming models, but the methods and techniques for painting vehicles are the exact same.
This is *not* my work, but it helps give the idea. Look at the skull on top of his banner pole. That's good highlighting between just 2 colors ("bone white" & some shade of brown.. forgot what its called), and then highlighted again with a touch of white. The results can be fantastic with a bit of practice.
