Yes, you can use a bed sheet as a budget friendly projection screen. You must make sure to keep the following factors in mind, 1. Make sure the bedsheet is a plain white colour. Try not to go for flimsy bed sheets as they do not remain stationery easily. 2. Cut it neatly into the desired size. 3. You can also add any other frame or pipe for stability. 4. Make sure to remove all the wrinkles and creases. Also make sure your sheet is still as possible without any movements.