Are indicated specific directions for our devotional prayers? For example N,S,W,E? what about Vishnu or Shiva or Devi practice?
If you wish to seek the relevance of these four directions then follow the discussions done between "Garuda" and "Galava" in "Bhagwat Yana Parva" of Mahabharat.
Garuda explains the relevance of all the 4 directions in very minute details, why they are named such and what should be the directions for all kinds of prayers (regular prayers, pitr-tarpan and others.)
The details are quite large, I hope they help you, please go through these sections.
Just to summarize:
Regular prayers (the usual ones) should be done facing east as it is the sacred direction as explained below:
That quarter towards which Surya the illuminator of the universe first riseth; where, at eve, the Sadhyas engage in their ascetic austerities; where that Intelligence, which pervades the whole universe first springeth; where the two eyes of Dharma, as well as he himself, are stationed; where the clarified butter first poured in sacrifice subsequently flowed all around; that quarter, O best of all regenerate persons, is the gate of Day and Time.