Can't beat that comprehensive list, but there's the Ingleton branch's Low Gill viaduct on the right as you reach the Lune gorge.
I find it easier coming south, but in clear weather you can see the Skiddaw massif over the Solway Firth at one point, also a glimpse of Helvellyn south of Penrith.
Preston-Glasgow - best fast run in the UK.
Plus all the high-speed curves (Weedon, Rugby, Rugeley, Whitmore etc).
Yes....forgot Low Gill viaduct. You can also see Blencathra (Saddleback) on the approach to Penrith....and as you correctly point out, in clear weather, Skiddaw is visible across the Solway Firth from Quintinshill to Kirtlebridge. On the right hand side, on the lower part of the descent from Shap Summit to Penrith, Cross Fell - and its slightly lower North Pennines neighbour Great Dun Fell, with its early warning radar station - are usually visible.
Many years ago, I used to kid my then girlfriend - now my wife - that Penrith Castle was deliberately built next to the station for the benefit of tourists arriving by train. Of course, she was unimpressed! The tower on top of Penrith Beacon used to be a prominent landmark on the East side of the line....but nowadays it has become concealed by the growth of the surrounding conifers and is no longer visible from the railway. I remember in days gone by at Christmas and Easter it used to have a large cross on the front, which was illuminated at night.
Another quirky lineside feature is - or was - the 'Australian Wood' on the hillside just North of Wamphray crossovers, midway between Lockerbie and Beattock. A smallish plantation of conifers on the hillside to the East of the railway, it was - according to Scottish railway colleagues - planted during the second world war by Aussie lumberjacks in the shape of their home country. However, in recent years I've had difficulty in identifying it from the train, so I am wondering whether it has been partially- or completely-felled.
The viaduct which carries the line over the Calder Water about a mile and a half North of Motherwell - on the direct line to Uddingston - has been known to generations of footplatemen as 'Babylon'. Apparently the weeping willow trees that grow on the embankments at either end of the viaduct are said to resemble the hanging gardens!
In the Winter - when there are no leaves on the trees - as you cross the viaduct over the Clyde between Uddingston and Newton, it's possible to get a brief glimpse of the ruins of Bothwell Castle, a mile or so to the South.
I could go on....but will try not to!
