From Kerbal Space Program Wiki
Hi, you recently uploaded three images. I have some suggestions for future uploads:
- Use a descriptive name. It doesn't need to be super precise as long as it unique.
- Use PNG to compress the images. KSP automatically creates screenshots as PNG files. The compression is lossless and you don't get those artefacts. Of course the files are larger, but as there are not many images uploaded this shouldn't be such a big problem. Editing is also lossless and doesn't decrease the image quality.
- Hide the GUI if you don't want to show any of the GUI. First GUI will be terribly compressed by JPG but apart from that they act like a distraction.
- And it is helpful to add categories.