There are no specific rules concerning acceptable postures while praying. But generally, the following are some Scriptural postures:
1. Kneeling in prayers, 1 Kings 8:54; 2 Chr. 6:13; Ps. 95:6; Isa. 45:23; Luke 22:41; Acts 7:60; 9:40; Eph. 3:14
2. Bowing in prayers, 2 Chro 29:29-30
3. Falling prostrate in prayers, Gen. 24:26, 52; Ex. 4:31; 12:27; Matt. 26:39; Mark 14:35
4. Spreading out the hands in prayers, 1Tim. 2:8; 1 Kings 8:22, 38, 54; Ps. 28:2; 63:4; 88:9
5. Standing up in prayers 1 Sam. 1:26; Lk 18:11-13; 1 Kings 8:14, 55; 2 Chr. 20:9; Mark 11:25
6. Closing the eyes while praying, Ezra 9:6; Luke 18:13-14