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

Other Hardware Displays
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char *names[12] = {
    "verbod1.bmp",
    "verbod2.bmp",
    "verbod3.bmp",
    "verbod4.bmp",
    "verbod5.bmp",
    "verbod6.bmp",
    "verbod7.bmp",
    "verbod8.bmp",
    "verbod9.bmp",
    "verbod10.bmp",
    "verbod11.bmp",
    "verbod12.bmp",
};
int which_number;

void loop(void)
{
  if (digitalRead(button) == LOW) {
      //note that arrays start at 0 e.g. 0 .. 11
      if  (++which_number > 11) which_number = 0; 
      drawBMP(names[which_number], 0, 0, BU_BMP);
      delay(1000);
  }
}

It is always wise to experiment with Serial.println() first. e.g. pressing a button and incrementing a number.

Hint. You need to choose a button pin. And use INPUT_PULLUP

David.