Question: What is one supposed to picture when praying since we may not picture Hashem (G-d) in a form and since He has no image?
Answer: Thank you for your questions. In Halacha it is stated that one should imagine the four lettered name of Hashem in front of him during prayer. This is why many prayer books (mostly Sefardic) have the name of Hashem writen in Torah script on the top of every page of the prayer book.
Rabbi Aaron Tendler