I made another one, and changed the pin-definitions a little.
As you can see I mounted the RFM95 upside down on the board as it makes soldering of the RFM95 and the Raspberry connector a lot easier. I also changed the NSS pin to GPIO3, and connected ground to pin 9. As a result, all soldering is done on the odd pins of the P1 connector (and on one cide of the interface board while all wiring is on the bottom side).
The result is quite OK, with just a minimum of cost. Assuming you have the Raspberry, its case, a memorycard and adapter already, the additional cost for gateway components is just 15 Euros or so.
Btw. I also updated the code of Thomas a little so it accepts DNS names for the MQTT server. Also I added the other TTN channels so this Gateway is working on a different channel than the previous one.