One thing I believe sometimes needs to be done is to correctly scale the circular objects. In some cases round planetary bodies are looking stretched or compressed like an egg and not completely circular. You'd need to use a paint program to do this.
This sucks because it really only affects round object like planets and moons! And that's what these screens are all about! Well..
This is how I've done it on some of my images.
1- Load the original image, rescale it close to 254x168, it is important to maintain the original aspect ratio, whatever it may be. You won't get 254x168 exactly. And it might work better doing it a little smaller. Just reduce one axis and let the paint program calculate the other axis. Thus retaining the original round shape and aspect ratio.
2- Now cut the shrunken planet out. It's smaller and still exactly circular at this time. And will remain so.
3- Reload the original image again. Resize it down to 254x168. Blot out the original planet and paste in the symmetrically resized planet from step 2.
Some images need this, some don't. It all depends on how close the original source image is to the 1.51 : 1 aspect ratio used on the Arrow's screens. This generally doesn't need to be done for crescent and partly lit planets, or status screens and graphs and text and charts.
Now if I can only make my images darker, more moodier, denser, and more monochromatic. I have a tendency (from art-photography hobby) to make everything bright and cheery!
Note: ..Must remember to make status screens with cleaner lines and green/red overall.