Yay!

What was that double-buffering thing?

Cool!

I didn't know that I could add buffers like that.
Now that it looks like the flashing is no longer an issue, I can start making a better game!

* How do I draw images/sub-images?

Take a look at the RPG sample.

   // Create the sub-image
    ImageSubrect tile;
    setImage(&tile, &img);

    tile.w = CELL_SIZE;
    tile.h = CELL_SIZE;
    tile.x = 0;
    tile.y = 0;
    tile.offset_x = CELL_SIZE * 3;
    tile.offset_y = CELL_SIZE * 2;

    drawImagesubrect(&tile, buffer);

edit 1:
* Also, could sub-images possibly be used as sprites?
I don't know what is exactly a sprite, but you can use it to draw tiles from a tileset, or to draw an animated sprite.
A sub-image is just like a frame on an image, where you can change its height, width and position.

I hope you understand me...

edit 2:
Sub-Images are like SDL_Rect in these tuto : http://vally8.free.fr/coinprog/sdl/tut5/sprite.php - http://www.aaroncox.net/tutorials/2dtutorials/sdl_sprite.pdf. But SDL_SetColorKey() doesn't exists yet.