Hi Andy,
The bezels for DW-6600 (nice watch!) and the DW-6900 are interchangeable so you have the option of finding a bezel you like either on eBay or elsewhere - tiktox.com are good people to check for bezels and straps. Alternatively you can go the stealth route which basically involves removing all the painted lettering and either leaving just the moulding or filling in with a dark grey. Or fill in with a bright colour.
My approach to modifying, on the very few I have done is to see what the market provides, hence my custom 6600 was a cheapie bought from Greece with a bezel and adapters from eBay and a strap from another eBay deal - though tiktox certainly used to have a range of cloth/velcro straps.
Alongside an official model the result looks almost as if designed by Casio (to my eyes anyway):
