depends on the snake, some can become quite stressed if they feel exposed, others may rub their noses on the glass, trying to leave the enclosure, and not being able to understand that glass is impenetrable, they will continue to do it to the point of doing damage to themselves. anything from decorative walls, to simple pieces of cardboard will help deal with this issue.
tbh the temperature instability is my biggest concern, glass enclosures cool and heat much faster than wood or plastic, and they do not distribute the heat of a UTH quite as well. Glass is also cold to the touch, which is another issue for a snake ability to thermoregulate.
White Polystyrene, although not as pretty as cork or fern walls, is an excellent way to maintain a more stable temperature inside a glass enclosure.
plastic enclosures solve all these problems without as much faffing about
wood is good too, for species which dont require to much humidity or for people handy with sealants and waterproofing varnishes