Transparent team picture gets dark background
I'd consider this a bug: if you upload a team picture with a transparent background (a PNG) then the picture's background will be dark, despite the UI around it being light. See attached screenshot. I'd expect a transparent PNG to remain transparent.
Uploading the same image with white background provides the expected result.
Sean Wilson commented
We're seeing this behavior as well.
Also the quality of the resizing is very bad. See https://microsoftteams.uservoice.com/forums/555103-public/suggestions/36051736-team-logo-resize-algorithm .
I would also consider this a bug. All transparencies are lost and replaced by black..
Zoltán Lehóczky commented
I'd also post the original PNG but I can't attach multiple files here.