FYIChangelog
BigCommerce no longer accepts WBMP and XBM product images
From 9 November, BigCommerce is gradually stopping product and variant image uploads in two old, rarely used formats: WBMP and XBM. Once the change reaches your store, uploading one of these files, in the control panel or through the API, gives an unsupported image format error. Images for modifiers, brands and categories aren't affected.