Hey Minus! I'll share what little advice I can, and hopefully some of it will be of use :)
If you're looking to improve your poses, I'd suggest first studying a bunch of different sources of official artwork of the pokemon you're trying to draw. Whenever I'm drawing a pokemon I haven't done before, I usually copy Ken Sugimori's artwork by hand first, and sometimes look at stills from the anime or manga before making rough sketches and original drawings; it tends to give me a better idea of that pokemon's anatomy, so that original drawings look more true to their actual appearance. Of course it looks like you're already doing that with Lugia here, but I think trying it out with some other pokemon (like Pikachu) would definitely benefit you!
Outside of that, the only thing I can think of immediately would be to try adding more shadows / highlights across the subjects. The bottom of Lugia's belly should be darker, and the front of it's thigh a bit lighter, for example (Though that's just what I see from looking at the official artwork; you could also try having the light source in a different position and draw the new highlights/shadows accordingly for some good practice).
I'd also like to mirror Sephirona's sentiments from way back and say that you did well with the unique pose of that Vileplume. It's also pretty cool how you have bits of red layered over the white lineart; gives it a sort of fractured appearance. If that makes sense :/ I like it though! :)
Hope this is helpful for you, keep up the good work!