Well I think it's a good first try. Looks like some depth blurring, nice colors in the sky as well.
One thing you might try, is using some antialiasing for the screenshot. It'll help smooth out th edges of the plane model quite abit, giving a more pleasant look.
I think the "jaggy edges" around the aircraft also have to do with your video settings in IL-2.
Some tips: play your game in settings it runs smooth and record a track.
Then play the track in highest possible settings (low FPS is less of a problem now, it's all about a nice shot) and take your screenshots.
Hey, something you might find useful (if you've got visited already) is this site: Screenshot Art.com
There are some super screen shot editor guys over there. If you drop by, tell them adlabs6 from Simmers Paint Shop sent you, I used to visit there quite often a couple years back.