Those files would be located in the /root/.emulationstation/themes/ Directory inside each theme so for simplelight in /root/.emulationstation/themes/simplelight/snes/art /root/.emulationstation/themes/simplelight/snes/sounds you should look up some guides about how people make custom themes for retropie im sure that would be step for step but you can just manually edit the files in those directories. dont change filenames around though.

I have a pretty foolproof and simple method that does not require to use te external pc.   Source https://github.com/sselph/scraper     Showing simplified method to quickly scrape artwork for Recalbox     Step 1.  Connect to your raspi.  On windows you can use putty  and just open a connection to your ip and use root for username  recalboxroot for password.   Or from a terminal client >ssh root@yourip   Step 2. Paste the following command > wget https://raw.githubusercontent.com/substring/fullscrape/master/fullscrape.sh && chmod u+x ./fullscrape.sh   Step 3.  Initiate an individual scrape request system by system For example to do SNES  see below > ./fullscrape.sh snes -no_thumb=true -max_width=375   To do nes > ./fullscrape.sh nes -no_thumb=true -max_width=375   Using the rom folder name as reference. Just a list of examples of systems you can use are   cavestory fba fbalibretro fds gamegear gb gba gbc gw lutro lynx mame mastersystem megadrive moonlight msx n64 neogeo ngp pcengine prboom psx scummvm sega32x segacd sg1000 snes vectrex virtualboy wswan     If you want to update or only add images that have not already been scraped you can do   > ./fullscrape.sh -u  -no_thumb=true -max_width=375     Things to keep in mind. To run the ./fullscrape.sh script you must be in the directory that you originally downloaded it to in the first step.   Image art is stored in the directory /root/.emulationstation/downloaded_images/ the gamelist.xml file is stored in the directory /root/.emulationstation/gamelists each in their respective named folder   if you run ./fullscrape.sh without the no thumb width flag it will download unvisible art for certain systems and you will need to delete that before scraping again as it will not overwrite correctly.  (This could be added as a pull request to github but may be a security feature)   WARNING : fba_libretro has a little bug, that will be corrected in 4.0.0 : scraping can’t be displayed. This can be manually solved if you really really are desperate …

Here is my method.  No need to use PC and you can do it all locally on the box.   Source https://github.com/sselph/scraper     Showing simplified method to quickly scrape artwork for Recalbox     Step 1.  Connect to your raspi.  On windows you can use putty  and just open a connection to your ip and use root for username  recalboxroot for password.   Or from a terminal client >ssh root@yourip   Step 2. Paste the following command > wget https://raw.githubusercontent.com/substring/fullscrape/master/fullscrape.sh && chmod u+x ./fullscrape.sh   Step 3.  Initiate an individual scrape request system by system For example to do SNES  see below > ./fullscrape.sh snes -no_thumb=true -max_width=375   To do nes > ./fullscrape.sh nes -no_thumb=true -max_width=375   Using the rom folder name as reference. Just a list of examples of systems you can use are   cavestory fba fbalibretro fds gamegear gb gba gbc gw lutro lynx mame mastersystem megadrive moonlight msx n64 neogeo ngp pcengine prboom psx scummvm sega32x segacd sg1000 snes vectrex virtualboy wswan     If you want to update or only add images that have not already been scraped you can do   > ./fullscrape.sh -u  -no_thumb=true -max_width=375     Things to keep in mind. To run the ./fullscrape.sh script you must be in the directory that you originally downloaded it to in the first step.   Image art is stored in the directory /root/.emulationstation/downloaded_images/ the gamelist.xml file is stored in the directory /root/.emulationstation/gamelists each in their respective named folder   if you run ./fullscrape.sh without the no thumb width flag it will download unvisible art for certain systems and you will need to delete that before scraping again as it will not overwrite correctly.  (This could be added as a pull request to github but may be a security feature)   WARNING : fba_libretro has a little bug, that will be corrected in 4.0.0 : scraping can’t be displayed. This can be manually solved if you really really are desperate …