Balcony Garden Beginnings

I've been slowly building a garden on our balcony. I collected a few pots during the last council hard rubbish collection and have been slowly figuring out what might be most useful. Although I started with a big planter box full of seedlings, I thought I'd be a bit clever and grow a few things from seed. But i wasn't clever enough to protect them from the birds who gobbled them as soon as they appeared. So I'm trying again with them, using some sheets of fish tank glass left behind by the previous tenant.

So far in seedlings I've got basil, coriander, thyme, chives, rosemary, mint and parsley. We planted a garlic clove that is going mental and I've planted seeds for rainbow chard, rocket and various types of lettuce.
I can't decide what else to plant in the big terracotta planter box. I'm thinking about leeks, strawberries, spring onions or something that climbs but I'm new to this and really have no clue what would work best.
Unfortunately the planter boxes are too big to hang off the railings but I did find today railing hangers for a couple of the round pots, which increases my garden size somewhat.

I'll post some more pics as it starts to look a bit better.