I can't think of house I have been to lately which didn't have a really nice modern mirror. You will find a mirror in almost every room of a house, and modern / minimilist style living has made the walls a blank canvas for you to express your personality.
If you use mirrors and artwork in the right combination – there is nothing to beat it. I find that the mirrors work best where they are functional, whereas the artwork can be placed on any walls which look bare – or just where it simply looks good.
There are many online stores offering cheap prices on both of these items, the main thing to watch out for is the quality. It is definately a case of cheapest not always being cheapest, ensure you are dealing with a reputable retailer.