Why 'fallen angel'? heading was angel. For me it's a star - a star can symbolise an angel but an angel doesn't symbolise a star. As a kid I used to see people's trees with an angel stuck on the top and think 'charming, stuff an angel on the top of a sharp pine tree so the tip is up its...' well, don't need to say the rest. Suffice to say it didn't seem right as a kid.

Having given it far too much thought, what I reckon you want is small trees with open canopies that don't shade the office too much. Birches would be fine, except that they grow too quickly. I started thinking of perhaps Prunus 'Amanogawa' (or Malus 'Van Eseltine') in the centre, with ten-year-old Chamaecyparis obtusa 'Nana' whose vivid green and shell-like swirls would make a superb contrast with the vertical, orangey wall - but you'd have to wait for them to make the impact. My best suggestion, though, is Acer griseum in the centre, whose peeling bark colours would blend perfectly with the wood walls but also soften them - its vivid autumn colours would give great anticipation through the summer. On the outsides, I'd have Eucalyptus niphophila, which also has striking bark, and its evergreen, sickle-shaped blue leaves would really complement and soften the office wall, and break up the strong edge all year round. You could plant under all three trees as neither species casts a heavy shade. Or, if you want to create a rhythm, stick with three 'Snow Gums'; but I quite like the idea of the 'Paperbark Maple' softening the centre of the double doors and bridging that big hole in the vertical planking. If you do this, please post a photo in ten years' time !

the tree would die eventually as it's not in a ideal environment being inside, and not to mention all the leaves you have to clear up and potentially dealing with tree pests. I love love trees but hate to see them misused in spaces or not given a thought to long term growth/maintenance

Don’t want to be a party pooper but no lollipop tree will stay that shape without regular pruning. So if you don’t want to have to climb up a ladder and prune a tree regularly, you may be better to get a dwarf tree or large shrub. I bought a tiny Photinia red Robin from Wilkos two years ago and it is huge now, about 8 ft, so will need some drastic pruning very soon. Depends how much work you want to put in. Smallish trees you could try are Crabapple, Hawthorn, Cornus, Magnolia and dwarf Apple Trees. Amelanchier is a beautiful smallish tree but even that will grow to 20 feet or so. Here’s my tiny Photinia, I’m sure it’s a Triffid!