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Jpg's don't support transparency. To remove the white background, open the jpg in photoshop or paint.net. Use the wizard tool to select the white background and delete it. Save it as a png. We're using a rectangular png logo and it worked for a while - until a bug in the last few days now adds a random background color. It's definitely a bug on Msft's end and I've posted here about it but support here doesn't seem to understand the problem so I'm submitting a service request to get it fixed.