If you want to make the curly brace a "Shape" you have to do it outside of Pages in a drawing program and bring it back in.
I presume you want to do this because you want to put an image inside of it or use a blend, there would be no other reason why you need this.
1. Open a Drawing program, see the list here:
http://www.freeforum101.com/iworktipsntrick/viewtopic.php?t=71&mforum=iworktipsn trick
2. Type the } character and outline it (turn it into a drawing)
3. Save it as a .svg file
4. Open it with
svg2key and convert it to a Keynote file
http://mcb.berkeley.edu/labs/zusman/dave/svg2key/
5. Open it in
Keynote and copy it from there into
Pages
If you just want it as a graphic, type it in a textbox as previously described and copy the box by command clicking on it, into the
Preview application which turns it into a pdf. Save that and bring it back into
Pages as a .pdf graphic.
Peter