Aside from the realistic value which painting can potentially offer, it helps to occlude damaging UV light which eventually compromises wood structure. As discussed in another question CRACKING is inherent with nearly all carvings. Painting a carving however will make cracks much more noticeable as crack fissures will show the natural wood color voids against the painted area of a carving. This will be especially evident with dark painted surfaces such as a black bear as it is contrasted with the color of natural light wood. Painting will require more maintenance to repair cracks and repaint areas which compromise the aesthetic value of a carving. Therefore painting is most successful only when a carving is dried thoroughly and cracking has been stabilized. On the other hand, leaving a carving natural will help make minor crack fissures less noticeable while also making it apparent your carving is indeed made out of wood. Some tree species such as walnut , cherry, and oak avail their true beauty when the wood grain is finely finished and displayed. Therefore, those subscribing to a rustic, traditional,  or natural feeling often find unpainted wood desirable. Maintenance is very minimal to natural wood but it is important to utilize quality sealers to protect the wood from UV light when carvings are positioned outdoors.  Finally, an effective compromise is a stain which contributes to the aesthetics of a sculpture while also affording the ease of maintenance and  protection from  sun and weather elements.