The only change was adding a new sky BG. The original sky was a bright blue clear day. I wanted a more subdue sky. Added snow turbulance, textured the engines etc. using Gimp.
I like to "dirty" the objects I do, to give a feel of working and everyday use.
Working with snow is very similar to working with water and waves. I customizes my brushes, started digital art about three years ago at screenshotworld.com ( aviation art).