Recommendation for simple Relay model?
An error "incorrect model type" is generated when the circuit element doesn't match the corresponding description in the .model statement.
E.g. in

M1 Nd Ng Ns 0 MyMOSFET         # M -&gt; circuit element is mosfet
model MyMOSFET NPN(Bf=75)      # NPN -&gt; model description of a NPN =/= mosfet


In OP's case, the manual states:


  Two types of switches are available: a voltage controlled switch (type S XXXXXX, model SW) and a current controlled switch (type W XXXXXXX, model CSW).


The error is due using a S type element, while specifying a CSW model.  

EDIT
From the manual:


  For the current
  controlled switch, the controlling current is that through the specified voltage source. The direction of positive controlling current flow is from the positive node, through the source, to the negative node.


So, put a voltage source in series with the inductor and name the source e.g. Vcoilcurrent.

.SUBCKT RELAY coila coilb common no nc L_coil=5mH            
* insert node coilc between coila and coilb
* and connect the inductor to coilc
LRelay    coila coilc L_coil

* and a 0V DC voltage source in series between coilb and coilc
Vcoilcurrent coilc coilb dc 0

* current controlled switches starts with a capital W
W1Relay common no Vcoilcurrent relaySwitchOn
W2Relay common nc Vcoilcurrent relaySwitchOff

* current controlled switches have a corresponding switch model: CSW
* do not use extreme values like 1n and 10G for the reasons given in chapter 3.2.15 Switch Model (SW/CSW) of manual
.model relaySwitchOn  CSW it=1m ih=0.2m ron=100     roff=100 Meg
.model relaySwitchOff CSW it=1m ih=0.2m ron=100 Meg roff=100            
.ends




Regarding the modelling of a relay:
I would use the parameters you normally find in the datasheet of a relay and implement those, so:


the coil resistance
the must operate voltage (minimum required voltage to turn on the relay)
the must release voltage (maximum voltage that will turn off the relay for sure)
maybe a fixed coil inductance (as it is most times not specified) of 10 - 100 mH to remind users to use a freewheel diode