Basically I'm trying to work out how I can add features to a dress I already own without it being permanent, or damaging the dress in any way, so I can wear the dress by itself again, and without them flapping off.

I am wanting to add windows, a sign and a St. john's ambulance sticker to make a TARDIS cosplay.

Will post further details and photos if possible in the morning when I'm on computer instead of phone! But thought that the sooner I posted, the sooner someone might respond!

Thanks in advance, all! X

Safety pins or a "tacking stitch" are the least effort options. But check the fabric first to see if pin-holes will close up afterwards.

Depending on where you want them, some sort of waistcoat or tabard might work instead. Or attach them to a belt maybe?

Thanks for the suggestions - have poked the back of the hem of my dress with pins, and they don't seem to leave marks, so as long as I use a reasonably small needle, it should be fine!

another option could be to make brooches of all the stuff you wanna add that way you don't have to resew everytime you wanna wear that cosplay all you need to do is repin brooches on

That's also an excellent idea, thank you! Will have a play with that once I've made the bits I want to attach!