Lost lilac - What should I replace it with?

Well anything really providing you have removed all the roots and revitalised the soil.

Do you want a shrub,small tree,herbaceous perenniels,roses what is the aspect sun or shade.

Sorry to be so vague but I think you need to be more precise as to you what you would like.

Mind, it is also quite likely that the lilac will have left a bit of itself behind and may grow again, so you might like to watch out for that.

Take you time about replanting if you can, renew the soil in the area, and look around at your neighbours planting, what do you love or not, look at public planting - often awful, but sometimes has interesting ideas.  

Lilac is so vigorous, I wouldn't write yours off just yet. I've cut mine back to ground level several times and she soon bounces back.....about 10ft tall & in flower at the mo.