I don't use a case with my X10, but I do use skins I got from ebay. You can also custom design your own skin with any photo. My pal is a Led Hed, so I designed a Zeppelin skin for his phone and he loves it.
Skinned, Un-Rooted Sensuous Black X10a that thinks it is an X10i running "Vanilla Gingerbread" 2.3.3 in Canada! Now Swyped from my 32GB Samsung Galaxy S3 running 4.4.2 (Kit-Kat) or Swyped from my Samsung Galaxy Mini (aka Dart)