[pkscout]

NVM, I think I must have messed something up, just reinstalled the addon, replaced '_' for '-' and it's working now
BTW, is there a way to include the root artist fanart to the slideshow? Only the ones on 'extrafanart' folder are getting displayed  

Yes there is.  In the slideshow section of the settings there is an option to include the root level fanart and folder files.  All that and more is explained on the Wiki page for AS (link in my sig). 😜  

 It was already toggled on but no luck. Anyway I read the wiki and it says the AS will copy the the fanart.png or folder.png to the extrafanart, but all my fanart are .jpg (the root and the obes on extrafanart) does it matters? 

No, the extension shouldn't matter. AS looks for .png, .jpg, .jpeg, and .gif files named fanart or folder.  If you post a log with debugging turned on for AS and Kodi with an artist who has the root level files, I can take a look.