On moeboru-based sites, such as yande.re and konachan.com all posts have images in both jpg and png formats. Currently, SzuruChrome only sees the jpg ones, so there is no way of importing the pngs.
Latest version should fix this (v0.10.1). I could only find PNG versions on konachan, so I can't guarantee that it also works on yande.re. If it doesn't work on yande.re then please reopen this and if possible also link to an example.
