How can I increase the brightness of photos on the HTC Wildfire S?
You can access advanced options to better configure your photos outcome and maybe improve them on that particular environment.



Open the menu panel to access and change camera settings:

To open the camera settings, while within the Camera application, press your device "menu" button.



Available Options:


Image adjustments 


  Slide your finger across each of the slider bars to adjust the
  exposure, contrast, saturation, and sharpness.

White balance


  White balance enables the camera to capture colors more
  accurately by adjusting to your current lighting
  environment.

ISO (photo mode only) 


  Choose an ISO level or set it back to Auto. Higher ISO
  numbers are better for taking pictures in low light
  conditions.

Auto enhance (photo mode only) 


  Select to reduce noise when using a high ISO setting and to
  automatically adjust photo brightness.




These are the most relevant settings to play with in order to obtain better results to your current scenario. You can read all about this and the remaining available settings on the users manual for your device under page 86.