180508.
Ah, that's understandable. Maybe when you feel more confident with your graphics, you may want to try blowing up the canvas to a larger size to work with. I mean the reason why some banner makers like smaller spaces is because it's easier to create a scenery with their c4ds in a cramped space. With larger canvases, you may risk going a little off tune and rhythm with the sort of things you want to do because of all the empty space you're not used to seeing.
But just the same, it's not impossible to try breaking out of the comfort zone, going bigger and making something out of that. It'd be great practice and a good way to show off your graphics on a more eye-catching level. One good thing about bigger canvases is that it gives you more room to show off. Graphics is all about showing off, making everything look spiffy and in tune, applying what you feel will make something look gorgeous and just showing everything off.
So with that point, whenever you feel like it, give it a try. :]