Kruziikrel13 updated Screenshot helper for 1.6.640 here, but both mods suffer the same issue of overwriting screenshots if they have the same name. This typically happens when you take a screenshot at the same in game minute. Now it will append a suffix (incrementing from 1) to the end of a screenshot if it shares the same name with another screenshot.
All credit to doodlum and kruziikrel13 for creating the mod and updating it to the latest game versions respectively.