I've been thinking of shed alterations too
I would like some changes to my shed as well.
A concrete floor that was flat and smooth, rather than something that was levelled with a long handled shovel and so has dips and hollows of up to 100mm, that would be good.
Walls that dont flex in and out when the wind blows, that don't let the rain blow in because they don't seal top and bottom. That would be even better.
When the day is young and the temperature is just above freezing it would be nice if there was a window to let in some sunlight and maybe some warmth - now that would be really good.
I think that this thread could give me ideas for real improvements. So keep those ideas coming.