It seems like the weather wallpaper widget doesn't handle requests to wettercom right. 
I just searched for the city I'm living using postal code 67433 and the right city (neustadt weinstraße) was found but if I click "OK" just the standard desktop is shown. 

I'm not really an expert doing this but I just analyzed the network traffic a bit using wireshark. This is what came out: 
for finding the location this get request is send to api.wetter.com: 
"GET /location/index/search/67433/project/weatherion/cs/5408d6b3deddae09492d56e05c75ecd5 HTTP/1.1"
The wetter.com server returns a xml file including this link: http://www.wetter.com/deutschland/neustadt/DE0007438.html which seems to be the right link to the webpage for my city. 

But as well a request to news.bbc.co.uk is send: "GET /weather/util/search/SearchResultsNode.xhtml?&search=67433&region=world&startIndex=0&count=500 HTTP/1.1\r\n"
But this one returns a site containing a note that no weather forecast could be found.

As well,  this file was requested: http://w1.weather.gov/xml/current_obs/index.xml

I hope this helps ;)



Reproducible: Always

Steps to Reproduce:
1. Choose any location from wettercom in the wallpaper settings.
2. Click OK
Actual Results:  
Just the standard desktop wallpaper is shown, noone specified in the weather settings.

Expected Results:  
The right wallpaper choosen for the weather of the location should be shown.