photoshoots should be easy - in the career rewards you'll find a working camera (followed Uni or NL, I think - and BV has a handheld digital camera). Just let a sim be the photographer, and let the model pose 

. There's probably a buyable version somewhere, and you can find photo lamps at MTS2. 
I'm pretty sure someone already made a Model career - my best guess would be to check either here at Insim, or at 
MTS2. (found two - 
here and 
here). 
I found some 
traffic cones that summons audience who either booooos or cheers for a chosen sim. (Simslice also have a bunch of other things that might come in handy. They're pay, but should be somewhere 
here)
catwalks are quite easy to build - as long as you've got the foundation walls (can't remember which EP they came with). There are several 
model pose boxes too.