Not much in the way of evergreens that are bunny safe. But as they aren't actually having access, a good option would be to mix some and some. Have some nice evergreen plants/shrubs and fill in around with plants that die back but are bunny edible.
Winter pansys (rabbit safe) would be a good option, but they need replacing annually - they do flower late and early and if it's mild all through winter. You could also add crocus bulbs (not edible) - they flower now but die back and disappear the rest of the year so good for planting between things to come up whilst they are brown/dead for winter.
Then you could have things like strawberries, which die back quite a bit in winter but are rabbit edible and look good din summer. Lots of herbs are bunny safe too and many will flower if you leave them to it. Nasturtiums would be a good option - although they are annuals they tend to self seed and if not are £1 a packet and you can sow them straight into the soil so very easy. They are really bright colours, rabbit edible, and will flower until the first frost.