the most suitable place of mandir in a flat/house/banglow is at north east(ishan kone)direction. We know about north east corner it is place of God and Goddess.
If there is no any separate room of pooja place than the room which is at north east corner you should keep there the picture of God/Goddess is northeast corner.
The different picture of God/Goddess should be kept in different direction.
North-God ganesha,Goddess lakshmi
North East - Shiv Parvati
East - Ramdarbar,vishhnu,laxmi
South east,South - Goddess dURGA
South South east - Hanuman
West South West - Guru Saibaba,jesus
North west- Pitar,purvaj