It is a picture taken from the LH
side towards the right of the main wheel well of a B737NG (note: missing standby hydraulic pump on the keelbeam and missing brake accumulator on the rear bulkhead).
Starting on the left of the picture, you'lll see the LH
aileron input torque tube and the two aileron PCUs. Beneath them is the "A" system electric motor driven hydraulic pump. Then follows the "A" hydraulic reservoir hanging from the ceiling (the big white cylinder). Beneath it is the "B" system electric motor driven hydraulic pump. On the keelbeam on the left is the power transfer unit (PTU) for the autoslat system (the cylindrical piece, where the two green pipes from the bottom go to).
Far back (still left) you can see the "B" system hydraulic reservoir. In the center rear of the picture there is the RH
MLG uplock hanging from the ceiling.
Going to the rear right of the picture in the upper far corner of the wheel well you can see the flap switch and valve module, which controls the flap drive (the green cylindrical piece from which the orange/black flap torque tubes run to the flap jackscrews). Above the flap drive module, there are the two brake metering valves (which on a B737NG are usually leaking). Below the flap drive on the keelbeam is the standby hydraulic reservoir.
In the lower RH
corner of the picture you'll see the standby hadraulic module, which contains the pressure filter of the standby hydraulic pump and the flight control shutoff valves for the standby system.
Mounted on the ceiling there are several valves of the brake system, like the autobrake and parking brake valves and the slat module (where you lockout the slats if you want to open the engine C-ducts)
The purple cylinders (like the ones on the keelbeam) are hydraulic fuses.