Hey Jonas,
this hasn’t been envisaged in the theme initially because in the absence of an image the text already present in the box should already contain some textual information. However, since it’s a rather simple customization, I can help out: please download this custom file I’ve prepared for you, unzip it, and upload the resulting file into the theme folder (/wp-content/themes/Ikebana/) replacing the existing one if prompted. Please let me know if it does the trick.
Sincerely,
Andrii / Satori Studio