Last year the disquieting images of Felix Vallotton filled the Sackler Gallderies of the Royal Academy of Arts (read ArtMuseLondon’s review here). This spring, another little-known artist, Belgian Léon Spilliaert is represented, in this the first major exhibition of his work in the UK. Like Vallotton world, Spilliaert’s is unsettling, but for different reasons. Plagued…