I'd like to use seven minute frosting for my cake but I need some design ideas how to decorate it. I know it is not an icing to really decorate with like buttercream . How do I decorate with this icing? is there anything that I can add to it to make it more stable and easier to pipe?

anyone please

Try a search of the forums for the following types of icings:

7-minute
Boiled
Meringue (not meringue buttercream)
Dominican
Suspiro

All of these have a similar base: whipped egg white and cooked sugar.

http://cakecentral.com/cake-decorating-ftopict-578965-.html&sid=159d2cb63c341d9a8c4389492b4e28a1

http://cakecentral.com/modules.php?name=Forums&file=viewtopic&t=685849&postdays=0&postorder=asc&&start=0

http://cakecentral.com/cake-decorating-ftopic-124291-next.html&sid=9ee32543b1c6ad15cc976f9b9fbe730c

A good site using this type of icing:

http://mariscakesenglish.blogspot.com/2009/11/suspiro-dominican-frosting-or-meringue.html