[bjornsundberg]

You can't see the pictures at all or you can't see them at the higher resolution?
I don't have a paid account so I can't test this myself. I actually don't use Picasa Web Albums, I use flickr

I can see the thumbnails but no picture shows up if the image is larger then 2049 pixels. Smaller pictures works great.
BTW - maybe you can use bigger pics on Picasa, if you have a gmail account you always have at least 1GB for lager Pics. I tryed Flickr but think they have way to slow upload speed.

Any hints on where I can see if there is any max supported pixelsize in the addon?

The addon doesn't have any maximum supported size, but the picasaweb api may limit the size.
The api was returning pictures at a fairly low resolution, so I recently devised a kind of url hack to get higher res photos for viewing. Most likely that is what is causing the high res pictures not to display. I'll see if I can upload some high res photos and test it. It may be that I'll have to use the old fairly low res versions for the higher res photos if I can't get them to work using the current method.

Ok, sounds like an idea. The photos works well on other apps that i think should use the same api. Did i mention I use this addon on IOS? I'm gonna test it on Max OSX later today.