For a designer whose clientele includes Germany's extravagant diva, Nina Hagen, ballet dancers, Olympic figure skaters and members of Russia's flamboyant fashion world, Katya Filippova's current exhibition at the Phoenix Cultural Center is relatively tame. Instead of her usual irreverent designs, this exhibit is a study in the range of classic Russian costumes. Her "Big Dress for Catherine," the showpiece of the exhibit, looks (and sounds) like it might have been designed for a Russian empress a century or two ago, with its heavy gold brocade jacket paired with a dark narrow velvet skirt and heavily ornamented velvet sash. But in fact Filippova says she thought of it as a dress for herself.The gown is just one of the several fanciful neoclassical dress models and retro accessories including medallions, sashes, shoes, and brooches the designer has decided to display in her personal costume collection.As a complement to the costumes, a collection of etchings are displayed on the walls of the gallery. This is the designer's first noncommercial, personal show. "This exhibit" says the artist/designer, clad in a black jacket with low velvet collar and a tiered chiffon skirt -- her own creations -- "shows where costume design and art meet. It is like my own personal museum." Filippova has made a temporary departure from the often pretentious world of Russian fashion design -- where she has already become an established figure -- in an attempt to reveal one of her "different faces, " faces that, in her opinion, every artist has. She clearly considers herself more of an artist than a simple fashion designer.For Filippova, 35, the real artistic mission of design is costume making.She studied book illustration at the Moscow Polygraphic Institute and her talent for painting did not go by unnoticed by her teachers. She says she went in for clothing design long before it became permissible during perestroika, and remembers adding humorous, baroque touches to military uniforms and to the brown outfits of young pioneers. Growing up during the Brezhnev era, when students had to abide by strict dress codes, she liked to make theatrical costumes. "I always liked to stay home and create fantastic clothes," she says.Some of Filippova's more radical reinterpretations of military uniforms made their way into exhibits and auctions abroad, where they were picked up by the likes of Nina Hagen. The designer admits that she puts together many unmixable items, but maintains that she is not avant-garde. "The avant-garde has already been established" she stresses. "Most of what you see that passes for avant-garde are just students' exercises who want to get cheap popularity." Instead, she would like to reach back to the great tradition of pre-revolutionary textile design and to the country's artistic heritage, some images of which are represented in her costumes and primitive figures of her etchings. The light, ethereal etchings often depict monochromatic figures selected from Russian folklore, Eastern pagan themes, and many images from the Russian Orthodox church. These are pictorial counterparts to the iconography she applies to her costumes. In the works, she uses images of gilt angels imprinted onto wisps of cornflower blue and black translucent chiffons draped over the heavier velvets and jacquard. She says her costumes are not supposed to have any place in transitory world of fashion and are conceived as museum pieces in their own right. And Filippova makes no pretension to represent any emerging trend of Russian fashion. "Now is the time for quality," she says. "There are many great Russian artists and designers who stay in their studios and make things with their hands. It is time for intelligent and cultured things to be shown."Her future collections, she says, might be still more ethereal and religious. She imagines a "Paradise" collection that could include costumes for Adam and Eve, or for angels eating forbidden fruit in Eden. But the present collection is just one phase of a tribute to the past.Referring to the display, Filippova says, "The tsar's family was a lot closer to God than Soviets wearing uniforms. But they were still on earth. Perhaps they could have worn these things."Filippova's exhibit runs until June 30 at the Phoenix Cultural Center, which is located at 3 Kutuzovsky Prospekt. Open 12 P.M. to 8 P.M. Closed Sunday. Tel. 243-4958. Nearest metro: Kievskaya.