I would mention those things in the context of telling them why you're a good "fit." When I wrote my letter of appeal to UCSD I first read their web site and made an outline of the things I know about San Diego. I then used aspects of my application, especially new accomplishments, to highlight how I fit their criteria.
Their admissions office told me to send it via email to the person whose name was on the rejection letter (Assistant Dean of Admissions, I think). Therefore I didn't really have a limit on the length. However, I have read elsewhere on SDN that letters of appeal should generally be kept to one page.
One other thing: use the same sorts of words they use on their web site and admissions publications. If they use a lot of warm, fuzzy words, then write about your "soft" qualities. If they talk about "investigating" and discovering" things, describe how you much love to learn. You get the picture....
Best of luck!!
SarahL 🙂