Just posting some pics showing two of my favourite models amongst my recently completed Ork army:

Some tips:

Metallic paint on cloth (Banner)? Normal people paint it grey.
Needs a bit clean-up.
You should paint more covering.
Washes is your friend.
Drybrush the Tin Bitz.

One thing i've noticed with alot of people's painted models is that they don't define well each of the separate features, for example on your mini the teeth are a good example where the bone/white colour has gotten onto both the lips and the recesses between the teeth, if you want a good looking model like GW stuff, just darkline the model.

Everyone has been praising the washes from GW ever since they came out and with good reason, they are awesome materials to darkline in a lazy way because they will settle in the recesses and darken a model so i think try some washes out and tidy up the model, it'll give a great effect on the metallics too. Personally i prefer the inks over washes as i like stronger pigments but the washes do a good job for painters of all skill levels.

PS: don't drybrush the whole model it'll leave a very messy finish in 90% of cases. Just do specific parts like the gun etc.

Err... nothing on those models has been drybrushed. I'd had a go at drybrushing the metal on some of my older models and it came out too gray so I didn't use it.

Beyond that the skin has been washed with Thraka Green.

I didn't mean to imply you drybrushed your model, it's just that it's the favourite tip on this forum from the majority of people except me who hates the technique ^^, but i think you should definitely check out black lining more as it'll help define the features of your models.