As of 0.7.6b you've fixed many of the battler pics but the sounds folder is still borked. Renaming Sounds and all folders beneath it to lowercase sorted all problems but one. sounds/outside/audio2.mp3 throws an error that it cant be found, because its actually under the "audio not used" folder beneath that.
Also as of 0.7.6b, chromium is throwing an error: 23[Intervention] Blocked attempt to create a WebMediaPlayer as there are too many WebMediaPlayers already in existence. See crbug.com/1144736#c27
Since it also threw the case sensitive error for basically everything in the sounds folder, on the initial screen, my guess is you are trying to load every sound clip at once instead of loading them as needed?