I recently decided that I needed MUCH more light inside of my snowmobile trailer (they only come with a small, single bulb "dome" light up front). So, I did some research and designed and built my own custom LED system. The results were fantastic. The amount of light I get from the "kit" I installed is more than enough for what I need - visibility for loading and unloading and the ability to see under the hood and make adjustments if necessary while in the trailer.
If anyone has an enclosed trailer and needs a custom lighting solution, let me know. I could design one for you as a DIY Install.
Here's a pic of the inside of my trailer, taken at night, no flash, on a dark and rainy night (no moonlight). While you can certainly see light in the background from the garage, that light does not illuminate the inside of the trailer at all.
For reference, I used two 5' sections and two 1.5' sections of light "bar" that I designed. If anyone is in search of a lighting solution, PM me to discuss what you need. I am able to produce a kit just like what I installed in my trailer for about $110 plus shipping. Installation time is literally 30 minutes or less.