The following works fine in Windows but when hosted on Linux, BYOND can't locate the file. Syntax issue?

if (fexists("images\\badges\\[g_listOfBadgeTypes[i]].PNG"))


Potential casing issue?

Googling, it looks like Linux uses forward-slashes for their file paths. Also, try adding a "./" to the beginning of your relative path.
In response to DarkCampainger
It was a casing issue. Windows doesn't care but Linux does. .png didn't work but .PNG did. Had to go through some hundred files and make sure they were all properly cased. I was unsure of file paths in .htm, .js, .css files so I updated those as well. So far so good.