How do I stop the model making it too neat?

Name the defect. Ask for glue shine, buckled paper, letters that shrink at the end of a line, or ink that has bled into the fibre. A general request for a handmade look returns a tidy illustration of one.

Is it acceptable to use a folk tradition that is not mine?

Name it rather than stripping it for parts, get the rules right, and for a real commission pay somebody from the tradition. Calavera, Madhubani and rosemaling all have living practitioners, and a generic borrowing is both worse work and worse manners.

Which of these is easiest to get right?

Crayon folk. It needs no craft knowledge, only a few specific imperfections, and it suits the small local events these posters are usually for.

Handmade and folk

Ways to make a poster that looks like a person made it, not a studio.

These styles all sit outside professional design, either because nobody trained the person who made them or because the tradition predates the profession. They are the strongest answer to a poster that looks generated, because the thing a model finds hardest to fake is a specific kind of clumsiness. Ask for the clumsiness by name and it lands.

Made by a child, or made to look it

Poster paint, sugar paper and wax crayon. Three ways of borrowing a child's hand, each with a different amount of design on top.

Child Paint with Pro Typography

A genuine child's poster paint picture, with sharp professional typography laid over it.

School Cutout Collage

Torn sugar paper stuck down with visible glue, cotton wool clouds and wonky letters.

Crayon Folk Handmade

Wax crayon on rough paper, drawn by somebody who is not a drawer.

Photocopier and scissors

The two tools of self-publishing. High contrast, no budget, and a deadline of tonight.

Punk Photocopied Fanzine

Third-generation photocopy: crushed blacks, ransom-note letters and everything slightly skewed.

Zine Cut-and-Paste

Everything literally stuck down: photocopies, tape, handwriting and typewriter slips.

Folk traditions

Four living traditions with fixed rules: what gets drawn, in what colours, and in what order. Older than graphic design and stronger than most of it.

Calavera

Skeletons doing ordinary things, cut as a relief print in black with hot flat colour.

Pennsylvania Dutch

Symmetrical folk motifs, hex stars and blackletter, drawn as a hand-illuminated certificate.

Madhubani

Every gap filled with pattern, figures with huge outlined eyes, and a double-ruled border.

Rosemaling

Flowing C and S scrolls of painted flowers, with a loaded brush and a visible highlight stroke.

Make one of them

Copy a prompt into an image model and pay for that one run. No subscription.

Open an image model

Other style groups

Graphic design movementsThe movements, and the wording that gets the look of each one.18 design movements Art movements as postersEach movement written as a poster the movement itself might have printed.21 art movements Print and reproduction looksThe printing processes, and the wording for what each does to ink.11 print processes Place and eraNational and period styles, each with the rules that made it local.14 regional styles Propaganda and protestPolitical traditions, and the visual rules each used to move people.7 political traditions Music scenesThe scenes, and the graphic rules each used to say who a night was for.10 music scenes Screen and digitalThe looks that came from a screen, and the wording that gets each one.10 digital looks

Drawing and render stylesDrawing a character rather than printing a sheet? The same reference, for how a picture is made.

Because the default output is smooth and competent. A specific kind of clumsiness, torn paper edges, crayon going past the line, a photocopy with no mid tones, is the fastest way out of that, and it reads as honest rather than as cheap.