Would using gravel-like rocks as a substrate be safe? They are very smooth and are about the size of a dime and I don't think a leo would really 'accidentally' swallow them. Here's a picture of the rocks I'm talking about, compared to a penny:
I agree, although it seems like that size gravel would be pretty safe, cleaning would be a pain. I'd advise putting a piece of tile in the spot your gecko(s) chooses as a poop corner to make things easier and having a second 'set' of substrate, as you will need to wash this to clean it.
It can also be a problem if you use too many with crickets hiding among them. I have a ceramic dish on the hot side of my tank with smooth pebbles that size in them (and a little sculpture of a gecko that some people take for the real thing) and the geckos like to sit on it and absorb the heat.
As others have mentioned, though there is no danger of ingestion, the rocks would need to be taken out and cleaned much more often (and more painstakingly) than other substrates. The glass floor of the cage would likely need to be cleaned as well. Feeders can escape and hide among the rocks, eat the feces, and eventually be caught by your gecko causing possible parasite overloads. It's simpler to have a solid substrate, but if you must use those, make sure to watch out for those problems.
Good points made. Also, it probably wouldn't be so comfortable on my geckos little feet haha. So I guess I won't. Anyone know of any other 'safe' substrates that I can use that look somewhat natural? (I use repticarpet now) Thanks!