if you really want to do something indoors theres loads you can do and they dont all need major amounts of resource,
2 of the most common ones would have to be water drops and smoke, very easy to do all you need is a camera, flash gun, a black bit of card and for water drops a tap,a bowl and either a coloured bit of plastic to line the bowl with or alternately food dye, or for smoke the only extra thing you need is incense sticks.
or you can easily try cross polarizing or creative bokeh, both fun things to do and can give off great results.