I want to do something similar to this image in a FBCT:

http://www.biblekids.eu/new_testament/lost_sheep/lost_sheep_coloring/lost_sheep_3.gif

I am wondering how big I would have to make it for the sheep in the distance to actually look like sheep, or at least so you can tell what they are supposed to be. This will be my first time doing a FBCT so I don't really know how small details can be. Could I put something like this on a 8" round or should I go with a 13x9 sheet, or what? Is there anything in this image that you can see would NOT work & if so why. TIA.

I would go with a 9x13 and use a small round tip in white to make little drops on the sheeps fur to make them look more like sheep. Then all you have to do is a black face and ta-da, sheep. I think the 8" round would be too tiny.

I would do a 13x9 as well. You will probably need to enlarge the image a little, but that would help give the sheep in the background a clearer look. You could also reduce the amount of sheep there are and make them slighter bigger.

http://cakecentral.com/gallery/78793

This is the most detailed FBCT I have made. I used a number 1 for the details. So detailed stuff can be done. You can also use a toothpick to kinda feather lines a little, when you don't want a full solid line but you are piping small lines.

I once tried to do a Baby Jaguar FBCT for my son's cake. It had a lot of detail, and I think above all, I was so concerned about getting the detail right that I piped the entire thing too thin. When it came time for me to flip it out onto the cake, I literally couldn't keep it frozen long enough to get it right, so it messed up horribly. So above all else, remember to get it thick enough so that it won't come apart on you.

Another thought - especially since sheep are fuzzy - perhaps you can correct any trouble with the tiny sheep once you flip the FBCT onto the cake? Just go back over them with a small tip to make them look like cotton and have a 3D effect. Just a thought. Good luck!!

Thank you everyone. I think I have a better idea of what to do now. Y'all are great!