Drill out the spot weld with a twist bit. This sort of controlled cut
limits the area of damage, but may not work if the welding left the metal
hardened, in which case use a hole saw slightly larger than the hardened
area, or a detail grinder or die grinder with a pointed stone.

If the welds are in an area covered with the art you want to save, work
from the back, rip away to your hearts content with any sort of
snips & tools. Shift to grinding as you get closer to the art would be more
controlled with less potential damage or distortion of the art surface than
tin
snips, etc.

Be sure to protect adjacent surfaces with wax coated screening, which I
presume you have in abundant supply.

JOhn

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