If you're looking to really create funky homescreens past the basic pre-installed style...then I'm sorry to say there is no "easy" way. But if you find homescreens that are close to what you are after, it becomes somewhat easy after one or two to modify the XML and accompaning images.
Microsoft has information on Smartyphone Plugins and Homescreen creation here:
http://msdn.microsoft.com/library/de...homescreen.asp
There is also a service that will allow you to create basic homescreens and send them to your phone over-the-air here:
http://www.smartphoneclub.net/
Microsoft also has a similar service specific to Verizon/AT&T phones but the link seems to be down at the moment, located here:
http://www.mywindowsmobile.com/
All pre-installed XML and images are usually in the IPSM/Windows folder.
This is a ROM folder and you can not add your own files here.
Homescreens and support files that you install should be placed in the IPSM/Application Data/Home folder. (2003 Users = Storage/Application Data/Home folder).
Give editing a basic layout a try and you will get better and better at it.
I can't write my own homescreens...but I can sure edit the heck out of others, customizing the XML and graphics to my tastes.
Have fun.