Maybe the fencing bent into a U was used for a trellis? It would probably be great for your cucumbers.
You could probably start your herbs now, if you were planning on using seeds. See the Winter Sowing thread on the Organic Practices forum here.
Your last frost date is about April 6, so you can plant earlier than I can.
You could start your tomato seeds in Feb/March if you have a warmish, sunny place indoors to get them started.
You could plant broccoli, lettuce and peas in mid-March directly, as they don't mind cool weather, then carrots and more lettuce in mid-April. The broccoli needs to be planted about a foot apart, but you could sow lettuce seeds fairly close around them, and harvest them before the broccoli starts spreading out.
Beans, cucumbers and squash could be planted direct after May 1, as they don't like much cold. For your smaller area, either train the cucumbers and squash on trellises, or plant bush varieties that don't take up so much space, and place them on the outside corners so they can spill outward.
You could start your squash and cucumbers in mid-April indoors, but they're sensitive to cold, so you couldn't plant them outdoors until early May. Don't start them with the tomatoes because they grow too fast. Putting some large rocks around their bases may help hold the heat from the sun.
If you want flowers, they might as well be edible.
Nasturtiums are great and add a peppery taste to salads, but they bloom better in poor soil, so maybe one of those corner boxes, or a whole separate pot with unimproved soil?
Calendula tends to have a spicy, peppery, sharp taste, something like saffron.
Borage has small, clear blue flowers that taste like cucumber in salads, and they really attract bees to help with the pollinating.
Pansies and violets tend to have a sweet, perfumy flavor, and they grow very easily here.
But just remember to have fun!
Sue