Having problems with Transferring Images for the bg

[Sick-_-boys]

So for a while, this wasn't a problem but it's interfering with like what I'm doing. Alright, so I have this image for a background, Its the right size, its "256 colors", and it's a bmp file... but apparently when I try to import the file it says the coloring isn't "256 colors". I have remade the same image so many times and messed with all the setting but it doesn't seem to work. I'm using gimp to edit the photo to "256 colors" and I made the art/bg in fire alpaca. I dont know what to do, I tried redownloading the programs to see if it would help and like nothing. Any advice?

 

[Poryg]

bmp? Images in rpg makers are png...

 

[Psychotic_Hero]

I use paint.net. Its free. just make sure to save it as 8-bit

 

[Kamillo]

GIMP has a bug - if you want save image in 8bit (256 colors) but your image have 16 colors or less - in this GIMP save image in 4bit 16 colors - RM2k/3 work only with 8bit pictures so rejects such pictures.

I prefer inrfanview for reduce colors palette.