It seems like during compilation a file called widget.css is created, which contains the css code of the the widgets. This leads to image display issues with the customSearch widget. Because the css is overwritten but the file is inside the widget folder. Also what is that 404.jpg with a cat on there being created upon each redeployment?
From version 2.5.1, widget CSS files are packed together for performance optimization. This means that widgets released prio 2.5.1 might use wrong file paths to embed images etc. Please check whether a 2.5.1 compatible version of the widget is released in the AppStore, or file a feature request.