You can often find decorative tins in charity shops, car boots and antiques fairs, but if you're not the thrifting type, you can still get hold of classic british brands in the supermarket (think Colmans, Lyle and Tate and Brasso). Don't forget to check the world food aisle too and look out for eye catching designs when you're on holiday.
Not to worry if you can't find tins with pretty designs on them. Make do with good old baked bean cans, remove the paper labels and paint in matte pastel shades and you still have rather fetching simple vases.
To introduce pattern, wrap the cans in clashing or co-ordinating giftwrap or wallpaper. The uniform shape and size of the tins used here brings a bit of harmony to this cheerful mix of colours and designs.
A cheap, fun and (perhaps with the exception of the spray paint) environmentally friendly way to decorate your tables.