Décor Guru John Derian on Avoiding the Hoarder Look

“My obsession with paper started when I was 20, at a flea market in Salem, where a dealer was getting rid of his business box by box,” said Mr. Derian, 55, who grew up in Watertown, Mass. “I couldn’t believe the prints were so old because they were so bright and colorful.” The creative one in a family of six kids, and a college dropout, Mr. Derian held a hodgepodge of jobs in Boston. At 25, he worked at a design shop co-owned by Apple Parish Bartlett, daughter of decorator Sister Parish (famously not a nun, she transformed the private rooms of the Kennedy White House). There he sold trinkets he’d assembled—lampshades made with chenille bedspreads, topiaries of buttons. In 1989, after a summer in New York, he was determined to stay. “I thought, ‘What could I do as a financial base? I’ll make plates.’” Within days he had $40,000 in orders for his decoupaged dishes.

The glue stuck. This week, his first collection for Designers Guild launched in Paris: wallpaper, fabric and accessories inspired by 2016’s best-selling “John Derian Picture Book.” We spoke with Mr. Derian about museums, antique finds that got away and papering walls with the printed word.

When designing their homes, people forget: the little things. The holder for your toothbrush, the stuff in the medicine cabinet. You see it every day, so why can’t it be beautiful?

The secret to displaying collections without looking hoarder-y is: put like things together so you see them as a unit rather than spread all over the house. I collect 19th-century wooden blocks people painted houses on, and when they’re together it strengthens that happy sense of wonder they evoke.

You don’t need a design degree to: move your furniture around, something I do constantly. It doesn’t take that long, and it makes you feel like you’re somewhere new. Last week I moved our living area to the dining room and dining to living.

My favorite source for original ephemera is: flea markets. I’ve only shopped online a few times—for prints from Panteek and Armenian food from Massis Bakery, on the street where I grew up. My dad’s parents were Armenians from Turkey.

My approach to mixing bed linens is: choose colors and prints you most relate to. I’m pretty neutral; I do tone on tone. I have quiet bedding but vintage throws for color.

In my house, I’d never have: a karaoke machine; friends bought me one and I exchanged it because it was ugly and big and not a game I had in my life. I haven’t had a TV in 15 years, but I like watching old movies on my computer. I binged 1995’s “Pride and Prejudice” with Colin Firth recently.

The most beautiful appliance ever designed is: a contemporary Wolf gas range—so simple and powerful. I had one in my last apartment. I’d put a flame on medium and use a camp toaster to toast all kinds of bread, which was really charming, but in my new place I have an electric stove and can’t.

I’m always looking for: a beautiful mirror ball from the early 20th century. I got one at a flea market—it looked like a flying saucer; you plugged it in and it spun. Someone bought it from my store. Normally I’m good at letting things go, but I still wish I had that.

People scared of wallpaper should know: in England most home stores sell wallpaper. It’s part of their culture. They put it up themselves, the way we line drawers with contact paper.

The most underappreciated museum is: the Merchant’s House, around the corner from my shops. An actual family lived there, and the home is intact. You can tour and see how they lived in the 1800s and rent the parlor and garden for parties. It’s more realistic than typical museums.

My first car was: a 1967 gray Ford Falcon my brother sold me. I had it for a year, the only car I ever owned. It had a wooden board as a fender but was really fun.

My most beloved houseplants are: geraniums. I have them in my sunny house in Provincetown. They get a glass of water once a week and flower all year round.

My favorite 1960s TV show was: “Bewitched.” It was magical and fantasy. I got the whole DVD box set and watched it recently. A lot happens in half an hour! When I visited friends in France in the early ’80s, it was a huge hit there.

The most shocking thing I ever sold was: a hollow, 2-foot winking head that was an ad for Buster Brown shoes and looked like Carol Channing. I wore it a couple of times but couldn’t see out of it.

One of my favorite DIY projects is: a hallway in my first New York apartment. I papered it with pages of six old, broken books, laying the sheets of mostly text out page by page. The palette, cream and black, was great. I brushed them on with a watered-down Elmer’s glue mixture.

The best era for ephemera was: the 19th century. Most of the etchings and lithographs I use are from then. It was the pre-photography era, and that was how you learned about things—the body, flowers, gemstones. Printmaking exploded then.

I’m always antiquing for: an oversize footed bowl, either stoneware or transfer ware. I have a fluted one I have a deep connection to, on my shelf protected like art. It’s 19th-century ironstone, wide and low. Which leads me to my pet peeve: a tight bowl. The food has no room to breathe!

—Edited from an interview by Kathryn O’Shea-Evans