the gemara says that the decorations don't battul a sukkah 10.tosofos, lefi daiiti, I think it says there is no Dirah Seruchah by decorations. according to the meztius I wouldn't want to have a ten teach sukkah with decorations hanging down. It's distracting.
Dear Elie,
The Rashba (Teshuvos 1:56) explains that if the decorations would have bothered the owner of the Sukah, then he would not have made the decorations! The fact that he made the decorations shows that for him it is not a Dirah Seruchah.
These objects don't create a lower Ohel/ceiling, and therefore the height remains ten Tefachim (Magen Avraham 633:7 in the name of the Shiltei Giborim).
All the best,
Reuven Weiner