Children don't have to make do with grown-ups' furnishings.

Downsized furniture, special storage systems, juvenile designs and accessories are available to help decorate children's rooms.Modular bedroom furniture that can be changed to suit changing tastes and needs of children as they grow and help them learn how to organize are being marketed by Room Plus Furniture. The modular systems include shelving, storage, bunks and desks that can be rearranged. Storage is included in headboards and trundle beds as well as shelves and desks. The storage headboard can be used at head or foot of the bed, as a toy chest or even as a window seat.

A small version of the classic fat tube bed, "My Little Bed" from The Newborne Company, comes in six colors (including "bubblegum pink") and uses a full-size crib mattress and bedding. Described as a transitional bed for children 18 months to 4 years, the bed is available with or without guard rails.

A similar "pre-bed" from "The Toddler Group" by Amisco comes with coordinating rocker, desk, table, chairs and telephone-pole clothes tree. Available in 17 colors, the group is made of double-welded tubular steel, with melamine tops for the desk and table.

White tubular metal and laminate furnishings with a European look are available for children and teens from Cosco. "Youth Options" includes tubular beds with optional trundle drawers, night stands, dressers, chests, armoires, chifferobes and desks. Handles have changeable cover plates in red or blue to coordinate with room color schemes.

The "DreamSheet," from Judi's Originals, is for the infant but may be more sharply appreciated by the parent who gets up at 3 a.m. to change a soiled crib sheet. The sheet set includes a fitted, moisture-proof bottom sheet and two top pads that attach with Velcro.

The baby's bedding can be changed quickly by peeling off the soiled top sheet and replacing it with a fresh sheet, without having to remove the bottom sheet and crib bumper.

The Lynn Hollyn Children's Garden Collection, like the designer's other work, evokes European classics. Her bedding and toy ensembles for infants and children include coordinating comforters, cushions, wall coverings, fabrics, rugs, stuffed toys, mobiles and wall art. "Good Morning/Good Night" is a fantasy design of bunnies, bears and elephants in bassinets suspended from the moon, and "Alphabet Romance" pictures bunnies and bears with books, learning their letters.

Five Disney character bed sets are available exclusively from Wamsutta/Pacific at fine chain stores across the country.

Washable, non-skid cotton scatter rugs with Disney characters - Mickey, Minnie, or Goofy - are from Couristan.

The children may want to emulate the grown-ups in calling in the decorators. A firm called Scrambles in Short Hills, N.J. (with franchises in the Northeast and Florida), is ready to design a child's room for prices averaging from $1,000 to $6,000. Designers help select fabric, colors, window treatments, murals, clothing poles, clocks, floor lamps, diaper pails and mirrors trimmed in fabric or wood appliques.

For purchase information, call:

Room Plus Furniture, 1 (800) 262-ROOM.

My Little Bed, the Newborne Company, 1 (800) 237-1712.

Amisco tubular bedroom furniture, 1 (418) 247-5025.

Youth Options, Cosco, 1 (812) 372-0141.

The Disney Collection, Wamsutta/Pacific Home Products, 1 (800) 344-2142 and Couristan, 1 (800) 223-6186.

Lynn Hollyn Children's Garden, Simmons Juvenile Products Company, 1 (414) 982-2140.

Scrambles, 1 (201) 379-6348.