You might have some success with custard type desserts too - chocolate creams made with milk, eggs, cocoa and sweetener can be really nice too, on same theme, vanilla ones and you can also get artifical flavours like coconut, etc, some health food stores may stock unsweetened dessert bases made from agar agar, you can sweeten them artificialy.
Don't forget just fruit, in moderation, stewed compotes and fools can be delicious and not too high in sugar, even though their quantities may be limited.