In my younger days maybe I could see the point of tinkering with how the OS is shown, or to change things around, but now I am happy with Windows Phone as it is.
The difference is in mind set now. If you want to tweak the Launch/Main Screen then Android is your goto OS. If you want lots of live information in Tile format then WP is it.
If Microsoft were to add a changeable feature, I would like something like the Dragon wallpaper on the Windows 8.1 ( Surface ) background. Something that scrolls up and down much like the background in 8.1 when you scroll side to side.
I think the addition of a few moving wallpapers would go a long way to calming the Custom Junkies jitters of not fully sold Android converts.
Windows Phone has grown out of it's Win CE days of custom every thing seen, for the "Live Tile/Information" Mind set now.
There is nothing wrong in wanting to dazzle up your OS, but if this is your major selling point...then Android is your thing now. It is a good OS and the phones are also good.
You can change roms with use of what the people over at XDA do, but with Windows Phone the only change you get is features built into the rom. Like Nokia Maps on an HTC.
Just basic changes....but your phone will look more or less the same.