This cable management clip is really slick. http://www.thingiverse.com/thing:620627
This fan cover gives your fans a little bling. http://www.thingiverse.com/thing:261115
I did have to run to the hardware store for some longer M3 screws, but that was well worth it.
Previous to these upgrades, the Y-axis wiring was drooping down to the print bed. For large values of X and Y, the wiring could scrape the object being printed.
I also like this spool holder, since I have the aluminum carry handle installed. http://www.thingiverse.com/thing:604386