Although it's nice to see custom props and materials instead of the usual HL2 stuff, it is also nice to investigate the possibilities of the default game material.
Take for example my map "Serene". It's huge in size, but has absolutely no custom content and the zip file is just over 5 MB. I'd rather download good maps with normal file sizes than a 80 MB file just because it has trees with green leaves and a new car model, for example.