How to program atmega2560 r3 with 3,5"tft for multiple pictures

It is always WISE to run the library examples first. Report any problems.

quote by name e.g. examples/Draw_SDCard_Bitmap

Then you can replace the example image with your BMP file.
Copy-paste your changed line(s) from Draw_SDCard_Bitmap.ino
Attach/upload your actual BMP file with editor icon #7

Then we can replicate your program / problem.

I don't want to guess what changes you have made. I just want you to tell me e.g. Draw_SDCard_Bitmap.ino

  //drawBMP("480Mouse.bmp", 0, 0, BU_BMP);
  drawBMP("verbod1.bmp", 0, 0, BU_BMP);

David.