One thing I always found would be interesting is if as your character levels, gains strength, constitution, battles enemies, etc, if that showed on your character. This would be a BIG undertaking, but for every battle, if your char got hit, there would be a chance of a random scar or mark to show up. As you level, and let's say, you up your strength score to give you another bonus when attack, your char looked a bit bulkier or wiry. Things like that. Changes that adventuring would bring naturally. Again, not expecting it, but would be interesting to see. Almost like a visual representation of the trials and tribulations your char has gone through on their adventures. First level chars are going to be a bit scrawny (by adventuring standards) due to their inexperience. As they level and grow, those indications of a veteran will begin to take shape.