Hi! I find that taking the same topics and just tweaking them slightly for a very specific demographic is helpful. So, ways to update your kitchen + millennials = a nifty piece on the trends millennials are looking for in a customized article just for them. Ways to repurpose barn wood + living in a small apartment = a customized piece on small barn wod projects that fit any space! You can always interview someone from that demographic. This method helps for SEO and for bringing new readers to your blog. Good luck!
I'd start with an informal reader survey. Talk to the "ideal" reader of your blog -- likely, you know these people personally. What questions do they have? What would they like answers to? What do they want to see more (or less) of?
Next, consider a formal reader survey. Michael Hyatt does a wonderful job and outlines his process here: http://michaelhyatt.com/tag/survey
I'm happy to help more. The answer to your question is right under your nose.
Look to the categories on your blog. For each category (like a chapter in a book), write down 5 topics you could address that answers a question of your reader or comments on your industry or shows how to do something. Do that for each category and you'll find you have the prompts for many posts. Feel free to connect if you would like to discuss further. I've been blogging and teaching clients to blog since 2004 so I have a lot to say about this!
Try to answer questions people have about home decor! Poll friends (or better yet, the readers on your blog) to find out what plagues/inspires them the most (kind of like what you did in your question by asking us about our favorite home decor topic). Troubleshooting, short cuts, DIY and personal stories about how you handled the same situation always has appeal. I'd also grab a few home decor magazines and see what those features look like. To answer your question, I'd like a slightly different angle -- cleaning. What's the point of home decor if the space is filled with clutter? ;-) Good luck and reach out if you'd like any help! I have three websites (two author sites and one foodie site) and have helped several others with their lifestyle/living blogs.