We are here to help you. But since it is regarding the picture size we cannot give you a fixed size as it completely depends on the user's picture content. I usual work with CorelDRAW and when transfer the file I take up this size in MSPaint 1448 x 1452 px for the coloring page and for the language worksheets the MSPaint pixel size is 1337 x 1636 px. Adding to it when you update them in the SVG site as attachment you got to choose the re-size value which could be roughly 1000 pixels or 1100 pixels. Make sure after choosing them they fit the whole screen in the PDF file.
These details I have given above are the sizing that I have learnt through my experience. However these things differ according to your picture content like I said before. Hence trail and error would be the preferred option. You learn out of your mistakes.
There are highlighted forum threads that you can look into for more verification. I have listed them here for you.
1.How to post Printables in StudyVillage
2.General instructions for all kinds of drawings
All the best. Let us know if you need any help
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