Welcome to Android Central forums. Like Golfdriver97 I have a few questions so we are all talking about the same thing and on the same page.
Was the phone smooth before, or like when you purchased it, and now it's laggy or slow?
Did you notice any change after removing the files?
Not as many questions as I thought I'd have... Anyway, if your issue is slow and laggy, like apps take longer to open, games/videos display with low frame rates, skip, jump, or freeze, that's more of a RAM issue as Golfdriver97 eluded to. Removing the images frees up ROM memory. This can speed things up a little but ROM mainly allows you to install more apps, take more pics and videos, anything related to saving something to the phone. While RAM affects how fast and smooth the phone acts and feels. It keeps videos and games playing smooth and affects how the phone performs. If this was your goal you need to look at what is using your RAM.
The best things to do to keep your phone running smoothly are things like, regular restarts. Restarting your phone regularly, from once a week to every few days. There's no need to restart daily, usually, but regular restarts have the benefits of clearing out caches, closing background apps and rebooting the OS and other systems on your device. If you find that you have one particular app that is slow or buggy, you may have to clear the cache specific to that app or take other steps specific to that app to improve the condition. Try to avoid Booster or Saver apps. Often times apps that claim they can increase your device speed or smooth operations have adverse affects and may not help with the issue much or at all. These types of apps often run in the background, using both your RAM and draining your battery. They usually come with ads, and if you buy the paid version drains your wallet too.
Let us know what you find and provide a few answers for better and more specific advice.