Appearance → Customize → Archive. Four settings: Show thumbnail, Thumbnail ratio, Thumbnail width, Thumbnail side.
Where the image comes from
Stoat resolves a listing thumbnail in this order:
- The post’s featured image, if it has one.
- Otherwise, the first image in the post content that is at least 300px wide.
- Otherwise, nothing — the row is printed with no figure at all, and the text takes the full width.
Step 2 is why an old blog with no featured images set still gets a picture beside each row. The 300px floor keeps an inline icon or a small logo from being promoted to a thumbnail.
To stop a particular post showing a picture, remove its featured image and make sure no image in the content is that wide. To stop it site-wide, turn Show thumbnail off.
Width
Thumbnail width takes either a pixel value or a percentage:
| 80px, 100px (default), 120px, 150px, 200px, 250px, 300px | a fixed size, whatever the row’s width |
| 20%, 25%, 30%, 40%, 50% of the row | tracks the row, so it scales with the content width |
The text column takes whatever is left. On mobile the thumbnail shrinks to 80% of the value you set — you do not configure that separately.
A percentage is the better answer when your listing is set to Full width: at 1170px a 100px thumbnail is a stamp, while 25% stays proportional.
Ratio
Images are cropped to fit the ratio, centred.
| 1:1 square | the default |
| 4:3, 3:2 landscape | the usual news-site choices |
| 16:9 widescreen | wide and cinematic; pairs with a wide thumbnail |
| 3:4, 2:3 portrait | for a photography or fashion site |
| Original ratio (no crop) | no cropping at all — every image keeps its own shape, and rows vary in height |
Original ratio is honest about the pictures but makes a ragged listing. Every other choice buys you a straight edge down the page at the cost of cropping somebody’s photograph — centred, so a subject at the edge of the frame can lose their head. If your images are mostly the same shape already, match the ratio to them and nothing is cropped.
Side
Thumbnail side — Right (default) or Left — is which side of the row the image takes. It also flips the featured first post hero.
On a phone the row stacks image-above-text regardless, so this is a desktop choice.
Image sizes served
The theme requests WordPress’s large size for a listing thumbnail and lets the browser pick from the srcset. Nothing is resized in the browser from a full-size original, so a listing of twenty posts is not a listing of twenty 4000px JPEGs — provided your uploads went through WordPress’s own image sizes. If you have changed those, Settings → Media is where they live.