To draw an image from the image list you'll typically use something like this:
DXImageList1.Items[0].Draw(DXDraw1.Surface,10,10,0);


To draw the same image with a different size you can do this:
DXImageList1.Items[0].StretchDraw(DXDraw1.Surface,Rect(200,200,250,250) ,0);

this allows you to draw your blocks the size you want when you want.

[PS. my experience is that StretchDraw can be very slow. If your images are a constant size in the game why not just set the Pattern Height and Width - which will then size your blocks as needed - will obviously only work if your blocks do not have textures.]