Last summer, Adobe killed their image exchange format "FXG". The idea was to have a publicly defined XML based image format which could handle vectors, bitmaps, and layers, and could be read and written by any app that wanted to support it (as Acorn did for a while).I can't say I'm sorry to see it go. It was a horrible format. The goal is worthy, but the implementation of it was an incredibly bad idea. When you want to send someone an image you want to pass them a single file, not an XML file with a folder of assets. While there are technical benefits to this, it's an incredible burden on the customer.
There is of course PSD which is the native format for Photoshop, and over the years it has become the de facto standard for layered images. PSD is a crazy format and implementing a reader and writer for PSD files is non-trivial and nobody but Adobe actually supports it correctly. It's crazy hard (and I'm not blaming Adobe or PS engineers for this- extending a file format for 25 years isn't exactly an easy thing to do).
So what would be better?