I am working on 3D printed enhancements for a number of loco kits which already exist.
Technology moves on in the DCC world more quickly than my developments. I am experimenting with a cradle to fit the hollow boiler described here. The cradle will hold a sugar cube speaker under the chimney and an LS4 sound decoder in the boiler. This arrangement looks like it will fit the SR Moguls, SECR E1, GWR Manor and 61xx and many other locos.
Here it is in the Mogul boiler ...
... and out of it
The cradle holds the decoder and speaker and acts as a restraint on the wires.
I am also working on chassis spacers to create split frames. The picture shows the SECR E1 with 3D printed ashpan and gearbox support, cylinder block, motion plate, crossheads and bogie frame. Nothing is fixed as yet. Modifications are needed but it is looking promising.
The E1 wheels have 3D printed centres, as described here, modified to fit the tyres from the late David Finney's Bespoke range.