It is not possible to specify an absolute file path (except for special folders like a plugin data folder – cf. Is this correct to use image fill) in plugins for XD. However, you can prompt the user to select a file and then use it as fill for an object as described in https://adobexdplatform.com/plugin-docs/reference/ImageFill.html.
From how I understand your use-case, you want to use an image distributed in the plugin folder, correct? If so, you can first use FileSystemProvider::getPluginFolder() (cf. https://adobexdplatform.com/plugin-docs/reference/uxp/module/storage.html#filesystemprovidergetpluginfolder-⇒-promisefolder) to get a reference to the plugin folder, then use folder.getEntry('Images/logo.png') on that folder reference to get a reference to your image and then use that reference like the imageFile in the ImageFill docs.
I hope this helps, if you need any further help, please feel free to say so 
Happy Coding,
Pablo