I'd like to see the BPG file-format supported in Opera (as well as other browsers), because of the superb compression algorithm compared to PNG/JPEG.
With BPG it's possible to reduce the file size of images dramatically, while maintaining better quality than other image formats. And thus reducing bandwidth and page loading times (when BPG is used instead of JPEG on websites).
Here's more info about the format: http://bellard.org/bpg/
Opera supporting it - or actually, Chromium supporting it since Opera uses the same rendering engine as Chromium - doesn't mean much. Both already support WebP which is also better than JPEG or PNG, but how many websites actually use WebP? Until websites use a format, browsers supporting that format makes no difference to bandwidth or loading times. (That is, you can only load what is there.)
I know that, but I think support should start somewhere. When major web browsers start supporting a format, en major design-software-vendors start supporting the same format, it may (or may not) get adopted. But there's no chance on adoption when there's no initial support.