AbandonedPorn

All the sites where this series is reposted say he was East German and initially started his "Abandoned" photo series in 1989 (after the Berlin wall fell) and had been adding to it at least until 2012 when a lot of his social media accounts went silent or started to disappear, so mid-90s or later is probably spot-on. Various sites also typically say "Abandoned buildings throughout Europe" or "more than 1000 buildings in Germany, France, Belgium, Italy, and Poland". It's possible he ventured into Russia, but these could easily be old East Germany or Poland.