I think Ashton & Juniper sound cute together. I agree with @Ehrob1 and @daisydarcy that the nicknames Dash and Ash might be too similar though.
(Feel free to mix and match these)
Callum & Elowen
Soren & Marigold
Harlan & Sylvie
Cyrus & Magnolia
Rowan & Hazel
Merritt & Calla
Ronan & Seren
Rafferty & Ophelia
Stellan & Cleo
Cormac & Willa
Jasper & Thalia
Emrys & Maeve
Everett & Junia
Silas & Zinnia
Jasper & Rosalie
Leander & Calliope
Lachlan & Olive
Hamish & Sierra
Hope this helps!