It should be noted that in any form of meditation, the body should be fully relaxed and not hindered. Whether full lotus, half lotus, or just crossed-legged is a matter of personal preference. A picture of Pa Auk Bhikkhu in meditative sitting posture is given here: http://www.paauk.org/images/PaAukPhotoAlbum/slides/Pa-Auk%20Sayadaw%20when%20young.html.
For example, in Myanmar sarong-clad practitioners would sit with their legs folded to their side because the sarong would hinder sitting in any lotus postures.
A picture of me training in anapanna is given here: http://www.facebook.com/photo.php?fbid=101913446508183&set=t.100000685852482&theater.
In Padmasan on solar eclipse 2010 over the Holy Narnada River, Asha Yogashram:
Further reading: A Revision of Meditation Methods by Bhante Seng is given here: http://fccheonghome.com/center/Q%20&%20A.htm.