Wiring a ceiling light with conductive tape?
The only way that's going to work (and all these are true there in Germany) is if 


the tape is fairly thick, because
the circuit is low voltage
the circuit has careful overcurrent protection on it
the circuit has arc-fault protection on it (which isn't terribly hard on DC and static DC loads like resistor limited LED lighting) 
The copper tape is only installed where out of reach of poking fingers or damage from normal activity. 


Have you checked each of the electrical sockets in your room?  It is common (especially in the US) for 1/2 of one receptacle (i.e. one socket of the two) to be swiched by the room's light switch.  This is done because it's about $30 cheaper in labor, x 3-4 rooms per house, x 2000 houses per development.  It is despicable and useless.  We usually go off to IKEA and get a simple $15 corner lamp to plug into that.  

Another option is to use a product like Legrand Wiremold (tm) to run surface conduit from that switched receptacle up the side of the wall.  Then you can either extend it to a room light, or to around-the-edge cove lighting, or to that copper system you propose.