There are several cases when you can upload an image with your edit/submission. These are pictures for albums, musicians and videos. I hope you understand that we can only accept images with a certain level of quality, so here are a few pointers for you:
1. For the love of God, never use Paint for working with images! Your best choice would be a professional image editing program, but in case you don't have one, there's a little free program called Irfanview
, which produces quite satisfactory results.
2. Make sure there are no borders on the sides of the image. Crop all unnecessary stuff. Make sure the contrast level is right, and the image is not too pale or too bright. Make sure there are no compression artefacts visible. Seriously, just make sure it looks perfect before submitting it.
3. Try to save images with lower file sizes but still a good quality. Keep the compression level at 50-60.
4. For videos, choose the most recognizable and memorable image from the video. Make sure it's not too messy and one can actually recognize what's on the picture. Try to keep the proportions - it's always better to crop the image than distort the proportions too much. Crop out channel logos and other redundant stuff as well.
If you feel you can't fulfill these requirements, it's better to submit an edit without an image, than with one that is poor quality.