I got the default folder .svg from my OS and edited it to add a paintbrush for my artwork folder and I place in in a separate icons folder saved as an .svg when I look at it in the folder it has a odd background/border. even though it has neither.
here's a link a screen shot of the image. I created it with inkscape from the original folder icon located in /usr/share/icons/humanity/places/48/folder.svg
If you look at the artwork icon in the home/pictures folder on the left it has that border. compared to the default just below it.
The svg(right top, displayed bellow showing transparency). I want to get rid of that border
