Thanks for the comment - I am curious - are you having problems getting your original images uploaded in the sense that they are too large (over 1mb)? Or is it just a cropping/resize issue?
We do now have an integrated re-size tool built within the editor, so any resizing can be done directly in the tool itself by clicking "Apply Effects and More" after uploading an image. This should allow you to perform your resizing outside of MSPaint.
Let me know!
Product Manager, Customer Marketing