In PS5 Scene news following the initial Custom BGM & Themes PS4 PKGs, PS4 Theme Sample & Base Template, BD-JB PS5 ELF Loader v1.2 and PS5 System Partition Read / Write (R/W) Payload comes some demonstration videos of the first Custom PS5 Themes including Background Music (BGM) of Hyperdimension Neptunia Theme v0.9 Beta from Ifaicompa (NepuStation3322's YouTube Channel) alongside a PS5 Just Do It Theme (PS5 BGM Change) from @yyoossk (Twitter / Yyoossk7821's YouTube Channel), a PS5 Elden Ring Custom Theme with PS5 Partition Mount (PS5PM) ELFs from @ifcompass (aka Ifaicompa), demo and Custom PS5 Theme Tools below from @master s9 via Twitter. 
Also below is a NMount PS5 System RW Source from Decompiler via @zecoxao on Twitter for those interested in source code examination of the recent PS5 system/system_ex R/W mounting.
From Pastebin.com: nmount PS5 system rw source from decompiler
The first custom theme for PS5
PS5 Partition mount (PS5PM) [The first PS5 custom theme] This payload will mount /preinst /system /system_data /system_ex /system_tmp /update partition directory as R/W
PS5 Just Do It Theme
PS5 Partition Mount v1.2 (PS5PM v1.2)

Also below is a NMount PS5 System RW Source from Decompiler via @zecoxao on Twitter for those interested in source code examination of the recent PS5 system/system_ex R/W mounting.
From Pastebin.com: nmount PS5 system rw source from decompiler
Code:
__int64 __fastcall _payload_base(_QWORD *arrayPointer, unsigned int *lengthPointer, __int64 string1, __int64 string2)
{
__int64 functionResult; // rax
_QWORD *str1Ptr; // rbx
__int64 strdupStr2; // rax
__int64 strlenStr2; // rax
int v10; // [rsp+2Ch] [rbp-14h]
int v11; // [rsp+2Ch] [rbp-14h]
functionResult = *lengthPointer;
if ( (int)functionResult >= 0 )
{
v10 = *lengthPointer;
*arrayPointer = realloc(*arrayPointer, 16LL * (int)(*lengthPointer + 2));
if ( *arrayPointer )
{
str1Ptr = (_QWORD *)(*arrayPointer + 16LL * v10);
*str1Ptr = strdup(string1);
*(_QWORD *)(*arrayPointer + 16LL * v10 + 8) = strlen(string1) + 1;
v11 = v10 + 1;
if ( string2 )
strdupStr2 = strdup(string2);
else
strdupStr2 = 0LL;
*(_QWORD *)(*arrayPointer + 16LL * v11) = strdupStr2;
if ( string2 )
strlenStr2 = strlen(string2) + 1;
else
strlenStr2 = 0LL;
*(_QWORD *)(*arrayPointer + 16LL * v11 + 8) = strlenStr2;
functionResult = (__int64)lengthPointer;
*lengthPointer = v11 + 1;
}
else
{
*lengthPointer = -1;
return perror("realloc");
}
}
return functionResult;
}
int __cdecl main(int argc, const char **argv, const char **envp)
{
unsigned int v4; // [rsp+4h] [rbp-Ch] BYREF
__int64 v5; // [rsp+8h] [rbp-8h] BYREF
v5 = 0LL;
v4 = 0;
_payload_base(&v5, &v4, (__int64)"fstype", (__int64)"exfatfs");
_payload_base(&v5, &v4, (__int64)"fspath", (__int64)"/system");
_payload_base(&v5, &v4, (__int64)"from", (__int64)"/dev/ssd0.system");
_payload_base(&v5, &v4, (__int64)"large", (__int64)"yes");
_payload_base(&v5, &v4, (__int64)"timezone", (__int64)"static");
_payload_base(&v5, &v4, (__int64)"async", 0LL);
_payload_base(&v5, &v4, (__int64)"ignoreacl", 0LL);
if ( !(unsigned int)nmount(v5, v4, 0x10000LL) )
return 0;
perror("nmount");
return 1;
}
PS5 Partition mount (PS5PM) [The first PS5 custom theme] This payload will mount /preinst /system /system_data /system_ex /system_tmp /update partition directory as R/W
- ELF & Theme Downloads: PS5 partition mount & custom theme (PS5 partition mount & custom theme.zip (108 MB) - includes PS5 Single Partition Mount Payloads: preinst.elf, system.elf, system_ex.elf and update.elf with PS5PM_v1.1.elf alongside Theme files PS5 Hyperdimension Neptunia Theme v1.0.zip and PS5 Hyperdimension Neptunia Theme v1.1.zip)
- Source code from: John Tornblom
PS5 Just Do It Theme
- PS5 Just do it thme.zip (31.3 MB)
- PS5 partition mount & custom theme.zip (185 MB - includes getpid.elf, mntinfo.elf, PS5 BD-JB ELF Loader v1.2.iso, remount.elf, preinst.elf, system.elf, system_ex.elf, update.elf, PS5PM_v1.1.elf, PS5 ELDEN RING Theme v1.1.zip, PS5 Hyperdimension Neptunia Theme v1.0.zip and PS5 Hyperdimension Neptunia Theme v1.1.zip)
- Theme file can be directly overwritten into the corresponding directory to take effect
- PS5_chainsaw_man_makima_custom_theme.zip (73.2 MB)
- PS5 payload loader.zip (48.9 KB) / Live Demo
- PS5 ThemesV1.00.Test.rar (171.49 MB - includes PS5 Themes.exe)
- PS5 ThemesV1.03.rar (184.91 MB)
- Payload⭐.zip (3.1 MB - includes preinst.elf, PS5PM_v1.1.elf, system.elf, system_ex.elf, update.elf, hardware_information.elf, list_all_files.elf, list_logs.elf, pipe_pirate.elf and process_view.elf)
- PS5 Theme Cyberpunk 2077 Multi-font version 1.0.zip (498.8 MB) / PS5 Theme Cyberpunk 2077 No Font No ⚡ Logo Version 1.0.zip (496.7 MB) / PS5 Theme Cyberpunk 2077 No Font Version 1.0.zip (496.7 MB) / Mega Folder
- PS5 Theme God of War Ragnarok - Raiden.zip (310.9 MB)
- PS5 Theme God of War - Burning Rage.zip (331.7 MB)
- PS5 ThemesV1.04.7z (224.99 MB)
- PS5 Theme God of War Ragnarok - Raiden.7z (288.2 MB)
- PS5Themes_GodofWarRagnarok+Font_V1.0.5.7z (393.6 MB)
PS5 Partition Mount v1.2 (PS5PM v1.2)
- PS5PM.v1.2.elf (649 KB)
- PS5ThemeFire.7z (139.86 MB)