Background Notes app allows you to embed text into images as note elements, then set the image as your Desktop Background.

As with other Note taking apps, be mindful what content you place as notes. Since background images have the potential to be seen from computer login screens, care should be considered.

-Click the + icon. Type in a text name for navigation item. Click "Add" button.
-Select newly create navigation item. This will load the view.
-Click "Choose Image" button in toolbar. Navigate to an image file and click "Open" button.
-The image will be placed into the view as a "background image".
-Click "Add Text". A new text element will be dropped center in the view. You may need to adjust scroll bars and/or click drag "Zoom" slider to see newly added text element.
-Click + Drag text element around to desired location.
-Double-click text element to open the text-editor sheet. Enter in desired text. Click "Complete" button when done.
-The "Scaling" button can be used to adjust the scaling of text elements. This can be useful for very large dimension images. Default 1.0 scaling will suffice for ~1920x1080 images. 
-Keep in mind text elements will be adjusted after change and they may inadvertently move to off view.
-Click the "Set Background" button to combine both the text+image content into an image and set it as Desktop Background.
-To remove a text element, right-click it and choose "Remove".
-To remove a text element that has been lost (e.g. offscreen), right-click the background image, select appropriate note from list and choose "Remove" or "Reset Position" (requires view refresh by clicking blank area of navigation view and then re-clicking navigation item) to bring the text element back to "center".