Hey, I just did some combination testing, and if my math is right, every possible dimension of the map is uniquely discernable to be a given tile size at given map size. This is CSV-style output, and can be read as:
If the map image is A pixels wide/tall, it is made of B tiles which are each C pixels wide/tall.
85, 17, 5
102, 17, 6
119, 17, 7
136, 17, 8
153, 17, 9
165, 33, 5
170, 17, 10
187, 17, 11
198, 33, 6
204, 17, 12
221, 17, 13
231, 33, 7
238, 17, 14
255, 17, 15
264, 33, 8
272, 17, 16
289, 17, 17
297, 33, 9
306, 17, 18
323, 17, 19
325, 65, 5
330, 33, 10
340, 17, 20
357, 17, 21
363, 33, 11
374, 17, 22
390, 65, 6
391, 17, 23
396, 33, 12
408, 17, 24
425, 17, 25
429, 33, 13
442, 17, 26
455, 65, 7
459, 17, 27
462, 33, 14
476, 17, 28
493, 17, 29
495, 33, 15
510, 17, 30
520, 65, 8
527, 17, 31
528, 33, 16
544, 17, 32
561, 33, 17
585, 65, 9
594, 33, 18
627, 33, 19
645, 129, 5
650, 65, 10
660, 33, 20
693, 33, 21
715, 65, 11
726, 33, 22
759, 33, 23
774, 129, 6
780, 65, 12
792, 33, 24
825, 33, 25
845, 65, 13
858, 33, 26
891, 33, 27
903, 129, 7
910, 65, 14
924, 33, 28
957, 33, 29
975, 65, 15
990, 33, 30
1023, 33, 31
1032, 129, 8
1040, 65, 16
1056, 33, 32
1105, 65, 17
1161, 129, 9
1170, 65, 18
1235, 65, 19
1285, 257, 5
1290, 129, 10
1300, 65, 20
1365, 65, 21
1419, 129, 11
1430, 65, 22
1495, 65, 23
1542, 257, 6
1548, 129, 12
1560, 65, 24
1625, 65, 25
1677, 129, 13
1690, 65, 26
1755, 65, 27
1799, 257, 7
1806, 129, 14
1820, 65, 28
1885, 65, 29
1935, 129, 15
1950, 65, 30
2015, 65, 31
2056, 257, 8
2064, 129, 16
2080, 65, 32
2193, 129, 17
2313, 257, 9
2322, 129, 18
2451, 129, 19
2570, 257, 10
2580, 129, 20
2709, 129, 21
2827, 257, 11
2838, 129, 22
2967, 129, 23
3084, 257, 12
3096, 129, 24
3225, 129, 25
3341, 257, 13
3354, 129, 26
3483, 129, 27
3598, 257, 14
3612, 129, 28
3741, 129, 29
3855, 257, 15
3870, 129, 30
3999, 129, 31
4112, 257, 16
4128, 129, 32
4369, 257, 17
4626, 257, 18
4883, 257, 19
5140, 257, 20
5397, 257, 21
5654, 257, 22
5911, 257, 23
6168, 257, 24
6425, 257, 25
6682, 257, 26
6939, 257, 27
7196, 257, 28
7453, 257, 29
7710, 257, 30
7967, 257, 31
8224, 257, 32