Cardboard Connection has a few additional variations listed. I don't know if we already know about these but chose to not include them or if they have not been asked about yet.
Cards 131 to 190 have either white card stock or gray card stock on the back. The images shown here are mostly white but some are gray.
Card 307 (Frank Campos) has either 2 red stars or 1 red star and 1 black star on the back on either side of words "TOPPS BASEBALL". The image shown has one of each color.
Cards 312 and 313 (Jackie Robinson and Bobby Thomson) have the stitches on the card number baseball on the back pointing both to the left and to the right like the Mickey Mantle variant.
Of course I don't have any actual evidence of any of this. (I only have 6 cards from this set.) Perhaps some of the 1952 Topps experts can confirm or refute these suggestions.
SJ