I have changed the .png file at below two locations with my logo
pi@VOXELSTUDIO:/usr/share/plymouth/themes/pix $ ls -ltr
total 16
-rw-r--r-- 1 root root 1286 Feb 21 13:46 pix.script
-rw-r--r-- 1 root root 187 Feb 21 13:46 pix.plymouth
-rw-r--r-- 1 root root 7496 Apr 13 01:59 splashscreen.png (my logo file renamed as splashscreen)
pi@VOXELSTUDIO:/usr/share/plymouth/themes/pix $
total 128
-rw-r--r-- 1 root root 232 Jun 27 2020 repetier_boot.service
-rw-r--r-- 1 pi pi 208 Jun 27 2020 mjpg_streamer.service
-rw-r--r-- 1 root root 532 Jun 27 2020 installLatestServer
-rw-r--r-- 1 root root 1851 Jun 27 2020 dhcpcd.conf
-rw-r--r-- 1 pi pi 755 Jun 27 2020 default.nginx
-rw-r--r-- 1 pi pi 127 Jun 27 2020 11-mjpg_streamer.rules
-rw-r--r-- 1 pi pi 669 Jun 27 2020 10-flash.rules
-rw-r--r-- 1 root root 190 Jun 27 2020 usb-mount.service
-rw-r--r-- 1 root root 192 Jun 27 2020 usb-mount3.service
-rw-r--r-- 1 root root 192 Jun 27 2020 usb-mount2.service
-rw-r--r-- 1 pi pi 218 Jun 27 2020 repetier_setup.service
-rw-r--r-- 1 pi pi 222 Jun 27 2020 repetierserver-perms
-rw-r--r-- 1 pi pi 1228 Jun 27 2020 repetier-network.xml
-rw-r--r-- 1 pi pi 650 Jun 27 2020 repetier-image-setup.txt
-rw-r--r-- 1 root root 47899 Sep 20 2020 splashscreen_orig.png
-rw-r--r-- 1 root root 264 Sep 20 2020 splashscreen.service
-rw-r--r-- 1 root root 1401 Jun 23 2022 wpa_supplicant-wlan0.conf.sample
-rw-r--r-- 1 root root 1456 Jul 8 2022 server-extra.xml
drwxr-xr-x 3 pi pi 4096 Apr 13 01:28 Logo
-rw-r--r-- 1 root root 7496 Apr 13 01:56 splashscreen.png (my logo file renamed as splashscreen)
pi@VOXELSTUDIO:/usr/local/Repetier-Set
But still after restarting raspberry I am still getting the old logo, please advise