Yes, you can draw everything to a PGraphics.

Code Example

1. PGraphics pg;
2.  
3. void setup() {
4.   size(500, 500);
5.   pg = createGraphics(200, 200, P2D);
6.   pg.beginDraw();
7.   pg.smooth();
8.   pg.noStroke();
9.   pg.background(255);
10.   pg.endDraw();
11. }
12.  
13. void draw() {
14.   background(0);
15.   drawPG();
16.   if (mousePressed) {
17.     image(pg, 150, 150);
18.   } else {
19.     image(pg, 0, 0, width, height);
20.   }
21. }
22.  
23. void drawPG() {
24.   pg.beginDraw();
25.   pg.fill(random(255),random(255),random(255));
26.   float r = random(pg.width/4, pg.width/2);
27.   pg.ellipse(random(pg.width), random(pg.height), r, r);
28.   pg.endDraw();
29. }