Blog images have one job: help the reader, or at minimum do not waste their attention. At 6 credits an image, generation makes it trivially cheap to put a picture at the top of every post, which is exactly why most blogs now have a decorative image that says nothing.
The useful version is narrower and cheaper than people assume.
TL;DR
- 6 credits an image on Seedream 5, 4 on Imagen 4 Fast. A year of weekly posts is under $4
- A decorative hero image is worse than none if it slows the page and says nothing
- Diagrams and screenshots beat illustrations for anything explanatory
- Alt text is an obligation, not an option. Describe the image, or mark it decorative
- Never generate a chart. Bars come out disproportionate to their labels
What it costs
Canon 8frame prices, a credit is $0.01 at pack rate:
| Task | Route | Credits |
|---|---|---|
| Hero image | Seedream 5 | 6 |
| Cheapest volume | Imagen 4 Fast | 4 |
| Image with correct text inside | Nano Banana Pro | 21 |
| Illustrative, non-photoreal | Reve | 34 |
| Adjust one | Flux Edit | 7 |
| Upscale for a large display | Clarity | 13 |
Fifty posts a year with ten candidates each: 3,000 credits, about $30. Which is to say the cost is not the constraint, and never was.
What actually helps a reader
In descending order of usefulness:
1. A screenshot of the thing you are describing. Free, specific, and more useful than any illustration. If the post is about a tool, a process or an interface, this is the answer.
2. A diagram. Three boxes and two arrows explain a concept better than an artistic interpretation of it. Nano Banana Pro at 21 credits when the labels must be right, or build it in any editor for nothing.
3. A real photograph of the real thing, if there is one.
4. A generated illustration, when the subject is abstract and there is nothing to photograph or screenshot.
Note that generation is fourth. That ordering is the honest one, and the reason most blog hero images add nothing is that people start at four.
Never generate a chart
Image models draw chart-shaped pictures with invented proportions: bars that are not proportional to their labels, pie segments that do not sum, trend lines that do not follow the values.
A reader looks at a chart and reads the visual relationship. If the visual disagrees with the data, you have misinformed them and they cannot tell. Make charts in a chart tool, free ones are excellent, then design around them.
Alt text
Every image needs alt text, and the two correct answers are different:
Informative images: describe what the image conveys, in a sentence. Not "hero image" and not the file name. If the image contains text, the alt text includes that text.
Purely decorative images: mark them as decorative, with an empty alt attribute, so screen readers skip them rather than announcing something meaningless.
The second case is worth sitting with. If the honest alt text for your hero image is "an abstract illustration of technology," the image is decorative, and the question becomes whether it should be there at all given what it costs in page weight.
Page weight is a real cost
A large hero image on every post slows the page, and page speed affects both readers and ranking. Generate at reasonable dimensions, compress, and do not upscale a blog image to print resolution for no reason.
If an image is decorative and heavy, removing it is a net improvement.
Consistency across a blog
The thing that makes a blog look like a publication rather than a series of posts: one visual approach, applied consistently.
Write a style block and reuse it verbatim in every prompt: "Flat editorial illustration, limited palette of slate and warm sand, no gradients, no photorealism, generous negative space." Save it with the model name and settings.
Most people lose their own best look because they never wrote down what produced it.
FAQ
How much do blog images cost? 6 credits each on Seedream 5, about $30 for a year of weekly posts with ten candidates apiece.
Do I need a hero image on every post? No. A decorative image that slows the page and says nothing is worse than none.
Can AI make my charts? No. Image models invent the proportions. Use a chart tool.
What goes in alt text? What the image conveys, in a sentence. Or mark it decorative if it conveys nothing.
Screenshot first, diagram second, generate fourth. The 8frame canvas is free and unlimited, and generation is paid from $19/month.