Specific image sizes are given when viewing that image in it's Collection page. (Via "IMAGE Collections" in the above menu). More generally though...
• "Single Shot" (ie NON panoramic) images:
These images have normally been either 26x39cm or 28.5x38.5cm - depending on their proportions. (Aprox 40x50cm when framed). Post 2012 though, with cameras producing much larger file sizes, the image is more typically 36x54cm.
• Panoramic images:
These much larger images are typically well over a metre in length. Their height between 30 and 40cm. Again, see the individual image page for details.
When mounted and framed a panorama will normally be around 60cm high and about 25cm longer than the image length.
That said, some panoramas are captured using an enormous number of individual shots thereby leading to a stitched image size of many GIGAbytes. These can also be available in still larger image sizes too. (Normally in an edition of just 5). Typically these are bought by corporate clients. For those images where this option is available, details are (again) given in the image's Collection page.