Come on then, let's see what extravagant designs everyone has done!
This game is based on a core high-speed route (using Eurostars) from London to Glasgow with branches and local networks, including local stations on the main route. As well as the trains, there is a single tram line serving Sheffield and linking to Chesterfield, a tram network in the West Midlands and a bus link from Darlington to Durham. There is also a shuttle bus Sunderland to Gateshead as the former station is closed due to low usage (as indicated by the crossed line on the routemap).
The junction in the screenshot is where my Manchester to London high-speed services join the core route (at the top), and where my Glasgow to Birmingham high-speed services leave the core route (to the left). The other two tracks are the slow lines for the Birmingham to Hull (via Leeds & York) service; the Glasgow to Birmingham services join this line at a junction to the left (not seen). You can also see the remains of the Nottingham to Leicester tramway. The high-speed route passes through Leicester without stopping as I closed the station because nobody was using it. The tramway was supposed to be a replacement but nobody used that either so I just left the tracks there! A few sections were removed whilst building this junction although the rest of it remains!
I've also uploaded a routemap I did in MS Paint; black lines are the high-speed services and local trains are in other colours. A single colour indicates a direct service, although not necessarily by the route shown (eg: Manchester - Birmingham services don't join the core route and then leave again moments later, they take a direct route through (not stopping at) Tamworth but the map shows the services and the stations they call at!