Need help turning this Random number method into a Random image method [on hold]

I have this method that generates these random numers with random colors that scroll down the screen as a part of this Alphabet Learning game. I need some help making it a Random image method rather than a random number method. Edit: I AM NOT ASKING FOR A COMPLETE SOLUTION, I JUST NEED SMALL BITS OF ADVICE

This is the code:

/*******************************************************************************    
*   randNum.java
*  Random Color, Number, Letter class to return a random .... anything
*It is used by Panel class and LearningLetterPanel class
*********************************************************************************/

import java.util.*;
import java.awt.*;

/*******************************************************************************    ********
   * This class is to be used for random numbers, letters, or colors
   * Using the Math.random class
    ************************************************************************************/

public class RandNum {
private String $alphabet="ABCDEFGHIJKLMNOPQRSTUVWXZY";
private int $width=640;

/***************************************************************************************
   * This class is to be used for random numbers
   * Using the Math.random class
    ************************************************************************************/
public int ranNum() {
        int $ranNumber = 20 + (int)(Math.random() * $width);
    return $ranNumber;
}
    /***************************************************************************************
       * This method is to be used for random letters
   * Using the Math.random class
    ************************************************************************************/
public String ranNumLetter() {
        int $ranNumLetter = 0 + (int)(Math.random() * 26);
    String $letter = $alphabet.substring($ranNumLetter, $ranNumLetter+1);
    return $letter;
}
/***************************************************************************************
   * This method is to be used for colors
   * Using the Math.random class for each of the three RGB
************************************************************************************/

public Color ranNumColor() {
    int $ranColorRed = 0 + (int)(Math.random() * 256);
    int $ranColorBlue = 0 + (int)(Math.random() * 256);
    int $ranColorGreen = 0 + (int)(Math.random() * 256);
    Color  c = new Color($ranColorRed, $ranColorBlue, $ranColorGreen);
   return c;
}
}//end of randNum