Currently huwiktionary's logo (shown in the upper right corner) is the on-wiki Wiki.png. It has no copyright data, so it should be deleted in favor of the Commons image Wiktionary-logo-hu.png (or its SVG version). However, first the wiki config should be changed to load the logo file from elsewhere, probably from Commons.
Why do you need VP announcement for modifying the URL of the logo without changing the image itself? I can delete the file right now without any config changes, just I’ll break the site.
The linked image is certainly transparent: on the page, its background is the same color as the page, if I hover over it in the Firefox inspector, it’s checkered, and if I open it as a standalone image, the background is solid gray (the default background color of Firefox for transparent images).