Flickr is slightly confusing in that they have multiple (undocumented) maximum file sizes. And in order to successfully upload and view an image the image has to meet all requirements.
First a file size limit, this is the one that’s generally documented (that said I think it should be in black and white on the upload page).
50 MB for Flickr Pro users
30 MB for free users
Second there’s an undocumented maximum pixel dimensions size (it may in fact be a memory limit on the Flickr server, but the effect is the same)
134 megapixels or smaller (11585 x 11585 pixels works, 11586 x 11586 does not). Note that this leaves some space between the two, but it’s a pretty narrow slice so I’m not worrying about it now. I feel good enough knowing that 134 megapixels or less will work, and I know I’m not downsizing panoramas much more than necessary at that size.
You’ll probably only run into these file sizes if you do a lot of panorama stitching, but it’s something I’m excited to try, so I wanted to be sure of the limits.