If you have a paid plan in Ideogram, you can use the search function, find t-shirt designs, edit and modify the prompts, and create brand new designs.
Ideogram makes this easy. You do have to have a paid plan. You can’t use this on the free version.
Ideogram T-Shirt Prompt Editing: How to Access Ideogram’s Search Feature (Paid Plan Required)
On the pricing page for Ideogram, it says search community images. Find inspiration from fellow Ideogram creators. You do have to have a paid plan to access this.

Step-by-step: Access the search and find designs

Ideogram T-Shirt Prompt Editing: Finding and Modifying T-Shirt Design Prompts
Once you have a design that you like, take the prompt and use it as a base to create new and unique designs.

Ideogram T-Shirt Prompt Editing: Using ChatGPT to Refine Ideogram Prompts
Come over to the free version of ChatGPT and use a simple instruction to keep the structure of the prompt intact while swapping key elements. For example:

Depending on the design, there might not be an animal, so you might not have to put animal. Use this as a base so that you can take other people’s prompts and create new and unique designs.
Please be aware that you do want to check your quotes to make sure they aren’t trademarked.
Ideogram T-Shirt Prompt Editing: Generating New Designs with Magic Prompt and Turbo Mode
Take the new prompt, copy it, come back over to Ideogram, and plug it in.
Recommended settings:

Click Generate and review the results.
Ideogram T-Shirt Prompt Editing: Analyzing Generated T-Shirt Designs and Making Improvements
Here’s how I evaluate and iterate:

New results can improve quickly. For example, Slow vibes only looked better, and some variations were even stronger.

Ideogram T-Shirt Prompt Editing: Adjusting Prompts for Backgrounds and Colors

If you keep getting different color backgrounds and you want it on a black background, ask ChatGPT for another, but also make the background black. Paste the updated prompt into Ideogram and generate again. Not every variation will turn out right, but you’ll usually find one that looks okay or better.
This is a real simple way to take other people’s designs available in Ideogram’s public gallery and then create more unique designs using the original prompt as a base. If you type in t-shirt in the search bar, there are many different types of designs you can do this on. You just need a paid plan in Ideogram.