Memory Usage of Sprites

It is expected If you are referencing the sprites directly.
This normally happens when your sprites are not in a Resources folder. In that case, the plugin has to add a reference to the sprites in the "Referenced Assets" section of the Localize component or the "Assets" tab in the I2Languages.prefab.
Given that they are referenced, then Unity loads them and keep them in memory.

To avoid this extra memory, move to the Resources folder all the sprites that change based on language.
When I2L finds a sprite in a Resources folder, it keeps its name and path instead of doing a reference. Then at runtime, whenever you try to use it by changing language, it just loads the sprite from the Resources folder. So, only the sprites of the current language are loaded in memory.

A third option is to use Bundles. In version 2.6.7f1 I added support for bundles.
In the Examples\Common\Script folder there is a class named RegisterBundlesManager.cs

That component, when attached to an object in your scene, it registers itself in the ResourcesManager and if the sprite can't be found in the Resources folder, the managers calls the LoadFromBundle function, allowing you to get the sprite from your bundles.

I also have scheduled for 2.6.8 to expand that example a bit and include a full bundle manager that could also download the bundle and re-localize things async once the requested assets are available.

Hope that helps,
Frank

So... if I put my files on resources folder I don't need to manually link them on References of the Localize? You just saved me days of work if this is true! =)

Yes, any file in the resources folder is saved as a path, so no need to reference them in the References section.

BTW, if you already have them in the references section, you will need to remove them from there once you move the sprites to the Resources folder. Otherwise, the sprites will still be referenced and always loaded.

Hope that helps!
Frank