Short answer is yes, provided they aren't listed in our exclusions (see list above). Feel free to add modifications and accessories at any time while you're insured with us – you don't have to let us know. So, if you want to get your car windows tinted while you hold a policy with us, they will be covered if you need to make a claim – provided the tinting has been done before you make a claim, of course.
Insurance stuff aside, all modifications and accessories need to be legal.
It might seem obvious, but if you make changes to your car that aren't legal, you could be fined, de-registered, impounded, and receive a defect notice. Doesn't sound fun, right? Make sure any mods are ticked off by your relevant licensing department before you get to work on your car.