I have tried changing the background, and selection bar images using just solid colored bitmaps. But all I get is a black screen at the code toggle page. do they need to be in a specific format, or bit depth?

This happen on generating again the rom and the output is different.

I think that is part of this issue a7fe52c, with this line the rom generated is broken and the output is the same when is generated twice (without that line).
This is part also of https://github.com/Mte90/GBAATM-Rebirth/blob/master/core/cheatcodes.cpp#L427

Probably there are some memory issues with the code, I am working on analyzing with valgrind and any tools that can help on improving the code.
Any help is appreciated because my experience with C++ is this project (and the original code is not mine).

In rom 0171 - Golden Sun (U)(Mode7).gba, when I input the cheats like this:

No Random Battles
3200047A 0000

Max Money
82000250 E0FF
82000252 05F5

The original GBAATM would generate correct cheat code in output file, but GBAATM-Rebirth generate it wrong. This can be check via cheat menu

Does not work anymore it seems!?

Freezes / crash -> game not patched but rom created...

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If you don't look up other users' experiences on the web, you don't know how it works
These include Execute every and VBLANK Check and DEADBEEF

Add in the first tab the checksum of the original rom and the generated version.

Require that the section gameinfo is removed to work.

[The biggest value ] 
Biggest=18543,FF;18545,FF;18547,FF;18549,FF;1854B,FF;1854D,FF 
 
[Highest-level ]
OK=1877C,FF 

[The biggest EXP] 
OK=18799,FF 

[Money] 
OK=1879C,1C,96,98

[Leading role HP]
ON=1854E,E7,03

[Leading role MP] 
ON=18550,E7,03

[Infinite red heart quantity]
ON=18794,FF

[Invincibility]
ON=0048c,0d

[All stage properties]
ON=187A0,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63,63

[All magic books]
ON=1883E,FF

[Alone with attack stage pro]
Dagger=1877E,01
Axe=1877E,02
Cross=1877E,03
Blue medical bottle=1877E,04
Holy book=1877E,05
knuckle =1877E,06
shurikien =1877E,07

[Completing the game time is zero]
ON=00088,00

[Entire whips]
ON=187bC,FF,FF

[Full magic list]
ON=1883F,FF,FF

[The enemy's information]
ON=18854,FF,FF,FF,FF,FF,FF,FF,FF,FF,FF,FF,FF,FF

[Sercet information]
ON=18843,FF,FF,FF,FF

[Condition]
Normal =1852E,00
Poisoned =1852E,01
Cursed 1 =1852E,02
Cursed 2 =1852E,03
Petrified 1 =1852E,04
Petrified 2 =1852E,05
Petrified 3 =1852E,06
Petrified 4 =1852E,07

[Fast upgrade]
Method 1 =1878C,FF
Method 2 =1878D,FF;1878C,FF
Method 3 =1878E,FF;1878D,FF;1878C,FF

[Walking speed]
Normal =18533,00
Slow =18533,01

[GameInfo]
Name=0612 - Castlevania - Harmony Of Dissonance (U)（恶魔城-白夜协奏曲）（E）A·RPG 64
System=GBA
Text=大胖子 整理提供

I believe it's 04000006, not 04000206 in vblank_int, and it's 16 bit, not 32 bit to use ldr r0,[r1]

As it is a new release maybe a new background can be interesting.

It is known that in the original GBAATM, it had an option to SRAM patch a game, for older flash carts that didn't handle other types. And we know that GBARunner2 only can handle SRAM saves, with the ability to patch some games automatically, but a few games, namely Golden Sun The Lost Age, needs it done manually.

Upon looking around, I'm unable to find anything within the code or comments stating that the new Rebirth version has SRAM patching. Will this be enabled in the near future as an optional feature, for those who use things like GBARunner2?

UX Suggestion:
When input GBA rom display (next to MD5 checksum):

• Region (USA/EU/JP) etc.
• Rom version (V1.0/V1.1) etc.
• Official rom ID

Add https://github.com/itay-grudev/SingleApplication to have just an unique instance.
The readme include the instruction and in our case require to change main.cpp

    What does the button [DEADBEEF] mean and do.
    What is the proper way to add cheats in the CheatCodes tab.
    Explain what the functions within the [Paramaters] do for example:
    - How is the menu text displayed within a game?
    - How do I know what RAM to use and what are the differences?
    - What is the difference between 1 / 255 cycles and what is the impact?
    - What happens when VBLANK Check is checked and not?
    - What does the trainer do?

From https://gbatemp.net/threads/gbaatm-rebirth-gba-auto-trainer-maker-a-new-hope.564321/#post-9122813, I think that I can improve the readme or add something inside the tool itself.

When I follow steps found online, the app crashes and disappears when I click "Patch Game"

OS: Windows 10 x64
GBAATM-Rebirth version: Pre-1.0.0 Alpha2
Games: multiple, but mostly tested with dumps from my pokemon games.