Although TT claims this feature is only available for the new models and the X40 series I noticed that you can change the Home icon for basically any V9 Navcore.
Here is the how to:
Create a BMP file of 32x32 pixels with a red background (the red will be transparent in the map view) and 24bit color depth.
Save the file as "althome.bmp" in the folder "skins" - if the folder does not exist you have to create it.
After the next start you enjoy your own custom Home icon.
Even if you can't really see it, it is my avatar, but be creative and do your own if you don't like it
Other icons that can be used to modify the look:
suspendtw.bmp - no idea what the difference to the standard suspend.bmp / suspendw.bmp is, root of the device
suspendntw.bmp - no idea what the difference to the standard suspend.bmp / suspendw.bmp is, root of the device
crowd.bmp - so far I can not find this icon for anything on my device
altfav.bmp - as above, gives you a different icon for the home address, folder "skins"
altbuddy.bmp - icon for your buddies, only works if you actually use the service "skins"
ClassCar.bmp - is accepted but can't see it anywhere LOL
antitheft.bmp - shutdown image, root of the device
antitheftw.bmp - shutdown image for widescreen devices, root of the device
splash.bmp - start image (comes after the boot), root of the device
splashw.bmp - start image for widescreen devices, root of the device
SafetyCam.bmp - should give a different icon for the TT cams but I don't use the TT cams anymore, folder "skins" or maybe in the map folder
horizon.bmp - this is claimed to change the view of the sky in the 3D map view but it seems not to be working, test if you like
ringtone.ogg - custom ringtone for your calls - copy into the root of your device
cr.ogg - not sure yet...
smsreceived.ogg - custom sound for receiving a SMS
suspend.ogg - shutdown sound
splash.ogg - startup sound
noautosuspend.dat - changes how the TT enters the suspend mode, just an empty textfile in the root
noautosuicide.dat - same as above but for total shut down, device should stay in stand by until battery flat
suicide.dat - textfile with a value inside, the value (in seconds) regulates after what time the TT goes from standby to fully off
All the files from other stuff go into the root of your device.
Using your TT a lot for hands free calling while on the road?
Tired of the crappy sound from the speaker making it hard to understand the other person because your car/van is noisy?
Just use the FM transmitter on devices that have it to redirect the internal speaker to your car stereo
Compatible devices are the X20 and X30 Series, since you can't access the NC10 based models I don't know how to use it on those.
I know the trick is very old but most people have forgotten about it.
If you do have a FM transmitter in your TT:
Create an empty textfile named enable_lineout_hands_free in the root of your device.
Make sure the file has no ending like .txt - just as above.
From now on all call will be coming through the FM transmitter, so you have to tune your stereo to the frequency you specified in the settings for your FM transmitter.
Have fun modifing the look of your TT!
As mentionened by tendriver some of the things won't work in other emulations than X40 or X50, that is due to the stupid limitations TT still includes in their Navcores...