How about spring star flower? They naturalize very well.

Kathy

Here is a link that might be useful: spring star flower

The 'blue' Anemone blanda might suit. So might hardy Scillas.

If you want "true blue" and inexpensive, try scilla siberica. These should spread quite quickly into a large patch under your quince. Ipheion is more pastel in colour and does not give you as much "bang for your buck". It has a shorter flowering time as well. Anemone blanda (blue) flowers a long time and is also a "true blue". It may need slightly more moisture and shade than the scilla, but in the right growing conditions is a great groundcover. I grow both scilla siberica and anemone blanda but cannot remember if they bloom at exactly the same time or not. There is also a vigorous white anemone blanda as well called 'White Splendour'.

Here is a link that might be useful: mass of scilla siberica