basement ceiling insulation

Gentlemen, I have a single story conventionally framed roof structure with 2X8 ceiling joists 24 inches on center spanning 16 feet. I also have 2X6 rafters 24 inches on center. I would like to strengthen the load capacity of the ceiling joists, but I cannot install more 2X8's in the 24 inch space between the original joists--too much stuff in the way. My question is, do you think laminating 16 foot 2X4's on top of the 2X8's would serve any use in terms of adding capacity? The laminated joist combination would then be around 11 inches of nominal vertical height. My other question relating to the rafters is, can the 2X6 rafters support 5/8 inch sheet rock with R13 insulation? The angled spans run 15 to 20 feet in various areas. I was going to add knee walls and collar ties so that the run between would never exceed 10 feet. I was going to use the space for seasonal storage and toy train layouts. There would be a carpet and pad load and a minimum of furniture load. I sure would appreciate whatever input you have on this project. Thanks, Jerry

I am currently finishing up my basement, and I am now cleaning the walls so that we can paint them over. I like the block wall look put we want to paint it. What should we use? The walls are already lightly painted white. Thank you for your response.