Quick Tip: How To Make a Desktop Computer and Table Lamp
The back row is black wool.
The table lamp is a glowstone with trapdoors, sitting on a nether fence.
The computer monitor is a painting placed on a stair block. You can remove the stair block and use a pressure plate instead, making it look like a laptop. But then you'll have a keyboard that's a pressure plate and the 'back' of the laptop as a pressure plate, it may not look pleasing.
The chair is a nether stair block.
The computer desk is two bookcases plus one wood plank.