(Red rules use only one criterion, blue rules combine two)

Very easy:

ABABABABABAB..... , AABBAABBAABB....., or similar basic patterns, where A and B can represent any of the binary criteria (man/woman, dead/alive, round/square picture frame, odd/even number etc.)

ABCABCABCABC....., AABBCCAABBCC....., or similar basic patterns, where A, B and C represent the three frame colours.

ABCDABCDABCD....., AABBCCDDAABBCCDD....., or similar basic patterns, where A, B, C and D represent the four background colours.
 

Easy:

AABABBABAABABBAB..... , AAABBAABBBAABB....., or similar slightly more intricate patterns, where A and B can represent any of the binary criteria (man/woman, dead/alive, round/square picture frame, odd/even number etc.).

AABCBCAABCBCAABCBC..... or similar slightly more intricate patterns, where A, B and C represent the three frame colours.

AABCDBCDAABCDBCD..... or similar slightly more intricate patterns, where A, B, C and D represent the four background colours.

ABCDABCDABCD..... or similar basic patterns, where A, B, C and D represent combinations of binary criteria (e.g. A = man alive, B = woman alive, C = man dead, D = woman dead).
 

Medium:

ABABABABABAB..... , AABBAABBAABB....., or similar basic patterns, where A and B represents a less than obvious binary criterion (e.g. "small number" (= 1 to 6) / "big number" (= 7 to 12).

ABABABABABAB..... , AABBAABBAABB....., or similar basic patterns, where A and B represent two background colours each (e.g. A = "warm colour" (yellow or pink), B = "cold colour" (green or blue).

AXXXAXXXAXXX....., AAXXXXXXAAXXXXXXAA..... or similar basic patterns, where A represents one of the four background colours and X any of the three other colours.

The new card must repeat either the background colour or the frame colour of the previous one (not both!).

The new card must repeat either the background colour or the frame colour of the previous one, or both.

The new card must repeat neither the background colour nor the frame colour of the previous one.

The new card must repeat either the frame shape or the frame colour of the previous one (not both!).

The new card must repeat either the frame shape or the frame colour of the previous one, or both.

The new card must repeat neither the frame shape nor the frame colour of the previous one.

Cards with pink backgrounds must always appear in pairs. Other background colours must never appear in pairs.

Cards with orange frames must always appear in pairs. Other frame colours must never appear in pairs.
 

Hard:

A > a, B > b, where A/B and a/b represent any two binary criteria (e.g. A = round frame, B = square frame, a = woman, b= man, so the rule would read: "After a round frame a woman must follow, after a square frame a man.")

A > a, B > b, C > c, D > d, where A, B, C, D represent combinations of two binary criteria (e.g.: A = man alive, B = woman alive, C = man dead, D = woman dead), and a, b, c, d the four background colours green, red, lila, brown. Thus the rule, in plain English, reads :"After man alive follows green, after woman alive pink, etc.)

1 - 4 > A, 5 - 9 > B, 10 - 12 > C, where A, B, C represent the three frame colours orange, turquoise, lila. ("After numbers 1 to 4 follows an orange frame, after 5 to 9 a turquoise frame" etc.)

ABBABBABBABB, where A is 3 or a multiple of 3 (i.e. 6, 9, 12), and B any other number. (Example: 7-8-3-1-4-9-11-2-12-5-10- 6 etc.)

The row of card is mentally divided in sections of three. In each section all three frame colours must be represented.

The row of card is mentally divided in sections of four. In each section all four background colours must be represented.
 

Nasty:

If the last two persons in the line face in the same direction, an even number is to follow. If they face in different directions, the following number must be odd.
Or, which is essentially the same:
If the last two persons are of the same sex, a dead person follows. If they are a woman and a man or vice versa, the following person is alive.

If the last three persons are of the same sex, a card with pink background is to follow. If they are not of the same sex, the background colour of the next card must not be pink.

If the last card has a number higher than the one preceeding it, a living person follows. If the last number is lower than the one before, the following person must be dead. No card must show the same number as its predecessor.
 
 

More to follow - please feel invited to send in your devious suggestions! Note that even the toughest rules become feasible if God gives suitable hints!