Yep. Many SMAPI mods support '[[Modding:Content_packs|content packs]]', which let you provide JSON text files, images, etc which they use. For example, you can [[Modding:Content Patcher|use Content Patcher]] to edit the game's images and data with zero programming needed. The rest of this guide is about creating a new SMAPI mod; for content packs, see [[Modding:Content Patcher]] (or the mod documentation if creating a content pack for a different mod).