When creating a logo/identity for your business, you don't always have to be to focused in showing what you do though a symbol or imagery too literally.
It's the obvious route which is why you'll have seen lots of piggy banks and wallets but say if you look at many of the world major banks, how many of them have an image or even a suggestion of money?
I can't think of many off the top of my head.
It's about creating something that your potential customers can connect with and you feel gets your image across.
This can be more about use of fonts, colours and abstract imagery.
More of a feeling really.
This is when it is good to employ a good designer that understands this.