The patio gets a blast of midday sun in the summer months so not really suitable for acers unless I move them about. Both acer attempts eventually ended up in the ground and are doing OK. PS Aldi was doing them cheap but I resisted.😇
I know an acer would look great but as I said it's not ideal. I really want something that you describe. Tall and weeping sounds good. But what? A dwarf something?
Here's a close up of Cotinus coggyria Golden Spirit @B3. A young plant will be happy in your pot for a year or two. If you want something more permanent, Carex Red Rooster has nice red/orange tones which you can accentuate with violas etc. (It would look better in your black pot!):
We have two Delphiniums growing in pots about that size. They are mainly in the shade with a little late afternoon sun. They are romping away and ,of course, disappear later on in the year.
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A glorious Acer palmatum..
or Acer palmatum dissectum...masses of named cultivars to choose from.
https://www.flickr.com/search/?text=acer&user_id=11713966@N02&album_search=1&view_all=1
https://www.google.com/search?q=acer+palmatum+dissectum&tbm=isch&ved=2ahUKEwir-6zCi97-AhXNpicCHQ4wCRAQ2-cCegQIABAA&oq=acer+palmatum+dissectum&gs_lcp=CgNpbWcQARgAMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDoKCAAQigUQsQMQQzoHCAAQigUQQ1DfBliCH2D3KmgAcAB4AIABiwGIAewIkgEDNy40mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=kupUZKvqI83NnsEPjuCkgAE&bih=595&biw=1280&client=firefox-b-d
PS Aldi was doing them cheap but I resisted.😇
You need something with height...something weeping in it.
Thinking.
Would be wasted with dwarf plants like Ophiopogon planiscarpus 'Nigrescens' IMO
A dwarf something?
Put some porridge in it.