I also like that idea and had some ideas on the subject:
Could have the characters body art change as certain stats are increased at a given value:
Strength adds muscle definition (start out smooth then 4 pack > 6 pack > 8 pack (if not pregnant or similar) - as base strength checkpoints are reached (strength from training not items).
Nimble makes the character look more athletic (With the current character art the arms would be 4/4 (high nimble) visual and the legs would be 1/4 (Low nimble).
Based on what I think is the case - 99 is an attribute's maximum:
1) Could have the change triggered by resting (blank the character art then display the updated character art).
2) The change points could be 20, 40, 60, 80.