A theme has to include an individual icon for each common application type, and then some more. The attached screenshot shows the 34 icons included in one theme. Note for example the two trashcan icons. I’ve seen as few as 33 (don’t know what was left out, maybe floppy48.png) and as many as 58.
Of course the hard part –graphically creating each icon which will be included in your theme-- I’ll leave up to your ingenuity. I just flinch them from the web. 
- icons for theme.png (58.38 KiB) Viewed 713 times
Download the attached template and extract it.
Right-Click the folder currently named my_icon-theme, select Rename from the popup menu and give it a new, unique name: one that hasn’t already been used for a theme available to Puppys. But don’t change the “-theme” part as Puppy’s pet creation application will use that as “version number”.
File-browse into RENAMED/usr/local/lib/X11/themes. Right-Click the my_icons folder and rename it to the name you’ve chosen, Don’t include “-theme”. Place your icons in the renamed folder. Leave that folder open.
Optional: 
Not required; but having one location where you can find the icons you want just makes life easier. Open another Rox-window to /RENAMED/usr/share/pixmaps. If there are any icons you want to have generally available when your theme is not being used:
Left-PRESS, Hold, then drag each icon from .../themes/RENAMED into /usr/share/pixmaps and select Link(relative) from the pop-up Menu.
If there are none, you can delete the /usr/share folder. Don’t delete the entire /usr folder. 
File-browse up until you see your RENAMED-theme folder as a folder. Right-Click it and select “create pet package”. If your Puppy doesn’t offer that option, click the ~ key to open a terminal at the parent folder of your RENAMED-theme and type “dir2pet NAME_OF_FOLDER” without the quote marks e.g. dir2pet RENAMED-theme. A pet will be created; in this example named RENAMED-theme.pet.
Theme pets are usually small enough to be uploaded to the Forum as an attachment. You can publish them by opening your web-browser to viewtopic.php?t=597. Click the Reply button to create a new post and give it a meaningful name, e.g., again using RENAMED as an example, RENAMED Icon theme. I recommend that you also post a screenshot of the contents to the /…/X11/themes/(YOUR RENAMED) if you actually want anyone to take the time to download and install them.