There is a trick that is very easy and practical to you can make a background sky with bright clouds without using cloud photo. You will use a feature called Smoke Map. Thus you do not need to rely on photo images. With Smoke folder, you can create a cloud creations themselves freely.
Here it is a guide:
Step 1
Open a 3DS Max file that you have
Figure 01. 3-Dimensional Objects
Step 2
Open Environment and Effects window also. None you change an option on Environment Map Smoke.
Figure 02. Smoke Elections Environment
You open the Material Editor window. Smoke drag the material into one of the slots in the Material Editor window (the same way as described in the previous trick). Set the parameter settings as shown below. Change Color # 1 with a light blue color and Color # 2 with white.
Figure 03. Smoke Parameter Settings
Perform calculations Render (click menu Rendering> Render> Render). You already have a bright cloud. Have a Nice Day! ;)
Figure 04 Results of Smoke Giving Environment