Basically u can make any shape in fibreglass, but ya gotta make a mould first. The old female/male thing.
Or you can use thin plywood as a base cut to the shapes you want then glass over them. Thin ply can be bent to slight curves but not complex ones, i.e. those that go in two directions.
Best to draw up what you want to do in 3 views and sections then make paper or cardboard templates. Bearing in mind that you will have to build in some MDF or thicker ply in flat sections to mount the speakers on. The pic u have shown looks very complicated and was probably made up in three seperate pieces then moulded together.
If thats what u want then be prepared for a lot of work and its very messy/dusty.
I have a good deal of DIY fibreglass so if ya wanna know more just ask.