Welcome to the site and to the 700wx!
I recommend you read
THIS thread first. You will find links to an app to be able to use PictureMail and many, many more cool things!
If you want to mod your Start bar you need Wisbar Advance 2 (
http://www.lakeridgesoftware.com). WALite only offers cascading menus and and a task manager.
The 'black' skin (I assume you mean the ones that kinda look like Windows Vista) is not provided with WA2, however, these are user-created skins so can be downloaded from the WA2 forums 99% of the time for free. I personally use
Vista Pocket 1.7. As a side note, the 700wx is a QVGA device, so remember to only use QVGA themes!
As for the background image you need to dowload a TSK theme, we have plenty on our themes forum, and you can ask for help on how to install them if you have any issues with it!
Once again, welcome!
EDIT: This inspired me to write a Wiki article about how to change Today themes, find it here:
http://wiki.ppcgeeks.com/index.php?title=Themes
This is the first one I've written ever, so feel welcomed to give me feedback.