You can add slow-worms - if you are very lucky! - which will eat slugs.
My son and I observed how the robin likes to perch on the spade handle to check for danger before he jumps down to forage for insects. So we made some robin perches and put them round the plot. Haven't seen him using any yet, but I'm sure the neighbours are scratching their heads!
Since your location is listed as the UK, I cannot be specific.
Native wildflowers are a great way to attract both the pollinators and the predators to your site.
A good mix usually has both annuals and perennials. Early/mid/late bloomers.
This keeps the critters around for the entire growing season, as well as providing abundant 'eye candy' for you.
Perhaps somebody like http://wildflower.co.uk/ has regional mixtures available.
I encourage all birds, and my garden is full of tall, slender bamboo 'perches'.
Thrushes are one of the few critters round here that will go for snails: make sure there's plenty of 'snail anvils' around the garden
Did I miss worms on your list?
Composters like centipedes, woodlice and springtails.
Flies-not houseflies and their maggoty ilk, but hover, drone, bee flies etc who do a great job pollinating around here.
Butterflies. They don't do an awful lot, but they're lovely to have around, and there's not all that many opportunities to insert words like 'metamorphosis' into conversations with kids!
Hoverflies and Long-legged flies are good to see as well. Field crickets are a mixed blessing, they do good work helping the compost cycle and controlling weed seeds, but can be pests on small seedling plants.
We're all out of roofs. But we still have tiny ads: