When screenschot is attached to bug, it appears as a small 178x100 pixels image. However, it is scaled down full size image (in my case 1379x940 pixels, 2.3MiB).
Attaching screenshots to bug report is quite common. If you generate thumbnails on server side, and use small image as a link to large image you would save a lot of traffic and time (for both you and your users). Scaled image in my case is 30KiB instead of 2.3MiB.
BTW, I love Bitbucket. You guys are awesome!