Buy (or even better, make) a wreath for each season. Celebrate changing the wreath as you prepare for and celebrate the High Days and the changes that occur in nature. Wreaths of greenery are available right now and are a good way to bring evergreens into your home. For Imbolc you might have a wreath of red, orange, and white bows, and then for Ostara a wreath with early spring flowers and colored eggs.
This works in a dormitory or a shared apartment as well – you can get little hangers that go over the door and hang the wreath inside! (I used to do this in the dorms at school. It always made my door stand out and look festive!) I actually use one of those hangers for my front door, since it has a large glass panel. You could also put a nail in the wall above your altar and make a tiny wreath as a rotating wall decoration.
For the Druid on a budget, check craft stores right around or just after the major holidays. Small grapevine wreath blanks are inexpensive, and once the major holiday is past, you can often get nice flowers and wreath decor for heavily discounted prices. I store my wreaths in an old packing box standing up on end with pieces of cardboard between them. Stalk the ribbon clearances as well!
If you’re lucky, you might even get birds nesting in the wreath! I watched a pair of wrens raise a clutch just outside our front door last year, and it was really very special.