A similar board is shown here:viewtopic.php?t=28426
So this should be a 512k ST? U32, U33, U34 and U38 look as if they are a different make of memory chip from the others so maybe someone had problems with this machine in the past and replaced those chips. Is this screen shown on boot? Video memory should start at $78000 on a half-meg ST so I think that the video memory would by default occupy memory chip U45 which is the same type as the majority of RAM chips on the board.
The display pattern is very regular repeating the same line every 160 bytes so maybe check the board for any track damage. Could it be that the video shifter chip is bad if there is no obvious track damage to the motherboard?
Still got, still working: Atari 4Mb STe, 520STFM, 2.5Mb STF.
Hardware: Cumana CSA 354, Ultimate Ripper, Blitz Turbo, Synchro Express II (US and UK Versions).