I don't do much in the way of pretty plants either.
Some varieties of peas and beans have very pretty flowers and don't look too different to sweet peas from a distance. I was just reading in the GYO mag that if you grow sweet peas amongst your beans it helps with pollination.
Swiss chard comes in various colours, I think the variety is Bright Lights and is a very attractive leafy plant with various shades of green to the leaves and the brightly coloured leaf veins. I am growing jerusalem artichokes this year for the first time and using them as a screen to hide a bit of garden we can't clear, there will be a usable crop too I hope.
I am sure other people will come up with more suggestions.