Are wireless chargers specific to model numbers? I found this charger on eBay:

http://www.ebay.ca/itm/Qi-Wireless-Charger-for-Samsung-Galaxy-S3-i9300-S4-i9500-Charging-Pad-Receiver-/200962957683?pt=US_Cell_Phone_PDA_Chargers&amp;var&amp;hash=item2eca536173&amp;_uhb=1

However, the model number of my Samsung Galaxy S4 is SGH-I337, which is not what's specified on the ad. 

Does the model number matter for wireless charging pads? Will the receiver for S4 i9500 also work on SGH-I337?

Thank you!
The model doesn't matter, but the protocol does.

The currently dominant standard is the Qi standard (pronounced "Chi") developed by the Wireless Power Consortium.  This is the standard used by the Nexus 4, 5, and 7, as well as the Galaxy S4, and several HTC, Motorola, and Nokia devices.

Other less used standards include Duracell's Powermat system and the Touchstone system used by Palm and HP.

None of these protocols are intercompatible.

As a general rule, anything Qi should work with anything else Qi, however it may not work well.  There are numerous shoddy charging pads on the market and the one you linked is probably one of them.  It appears identical to one I purchased and it does not function well.  The range is poor (It won't charge through a case of any kind) and it charges very slowly.  I can't speak for the quality of the receiver they offer though.