It happens to me sometimes. I get round it by drawing shapes, in different ways (eg blindfolded, using left hand, left and right hands together, using natural objects like pebbles and branches as suggestions for forms and templates) Sometimes nothing more than a simple line can spark a creative idea. Boat builders know when the form is fair.....
Look at photos of old pottery such as neolithic or mediaeval german, or better still English.... HUGE varieties of the same basic forms. Then you could consider drastic changes by using texture/color on carved items. Or consider doing a BIG carving. Or simply do a copy of a carved thing you like that was made by someone else, or try doing a carving in an unfamiliar style. Clothes hooks, spades/shovels (those are great to do...!) Mini canoes, pike lures.....name plates, house signs