Maybe the directory here for file uploads doesn't have the correct permission. I'll check about that. I'm going to try to attach a small image here to see what happens.
About the Fivealive backgrounds, etc., it was kind of tricky to have a gradient image work OK with a solid background color. If I recall correctly, originally the image with the gradient was wider, but it got reduced maybe to decrease the file size, I'm not sure. If there is a significant problem for certain logo sizes, maybe it should be looked at again. On the other hand, I don't think these more or less general-use themes can be expected to accommodate every logo size, and in some cases it might be more reasonable to resize the logo to fit the constraints of the theme's design. Anyway, we can look at it when the info is here.