I can't find a pic of a shell-curled specimen. But, here's some info on shell curl. Most from the Veterinary Network. Some from me:
Metabolic bone disease (MBD)
The clinical signs of MBD in chelonia depend upon the stage of shell development which is affected by the disease. If the young growing chelonian is maintained on an inadequate diet the shell may fail to calcify and so remain soft, rather than becoming firm at around 12 months of age. The muscles of the pectoral (shoulders) and pelvic (hips) girdles pull on the relatively weak shell as the disease progresses. The rear end of the carapace is pulled downwards and the carapace edges curl upwards. MBD is implicated in the cause of pyramidal shell growth of turtles. As the turtle continues to grow, it begins to look too small for its shell. The scutes show uneven growth. The animal will also show reduced weight gain, small size for age and overgrowth of rhamphotheca (beak) and claws. The turtle may also have difficulty lifting the shell from the ground when walking.
MBD is more difficult to diagnose in the turtle or tortoise which has already formed a normal shell. An adult chelonian presenting with a history of a deficient diet, broken bones, anorexia and lethargy is suspicious of MBD. If the animal has been affected for a longer period, the carapace may curl at the edges and the animal will appear small for its shell. The bridge can grow abnormally; rather than horizontally its grows vertically. This increases the distance between the carapace and the plastron. Diagnosis of MBD requires radiography of the whole chelonian. The bones will show decreased opacity, especially in the pelvic (hip) and pectoral (shoulder) regions in the early stages progressing to irregular cortical thickening of soft tissue density (fibrous osteodystrophy) in the later stages.
MBD is fatal without the appropriate treatment. The disease takes months or years to produce clinical signs and so often requires months of treatment when it is presented to the veterinarian. Caring for and treating an animal with MBD requires patience and dedication on the part of the owner, working in partnership with the vet. Mild cases of fibrous osteodystrophy can cure completely but more severe cases may be left with permanent changes. The husbandry, especially the diet, must be corrected for treatment to be successful.
When FRTs develop shell curl (MBD) it doesn't simply alter their appearance. The curl also distorts the interior of the carapace, distorts the normal architecture of the skeleton (can lead to reduced range of motion), and places pressure on internal organs within the area of distortion.