Would like to tile the bathtub surround area including the ceiling. Will I have any problems with the tiles staying on the ceiling while they are setting?;)

Only The Ones You Let Go Of! Lol Use Thinset Mortar And Mix Some Calcium With It. Also Keep It A little Thick, This Will Help It Stick Faster.
One Thing To Keep In Mind If This Is Going To Be Inclosed Then You May Need To Slope The Roof So Moisture Doesn't Build Up.
Other Than This Your Fine To Do It. Take Your Time With It. As Far As Size Of Tile On The Ceiling I Don't Think Id Go More Than 6x6
If You Go Bigger Than That What You Can Do, And You Can Do This For Any Size If It Makes You Sleep Better. Once You Lay The Tile. Cut You A Few Pieces Of Wood 2x4s Not Tight But Say 1/4 Shy. Lay These On Each Row, And Then Cut Some Supports From The Edge Of The Tub To The 2x4s Be Sure To Place Something On The Tub To Help Not Scratch It Up.
Hope This Helps