A Christmas banner can be a fun blog decoration. You don't have to use an entirely new theme. This can really be a way to get a new look for the holidays without doing a lot of the coding yourself. As with any time of year it's really important to make sure that you get a cohesive look on your blog. This can even be professional looking enough to use for a store or business.
Try to dress up your basic logo. An easy way to do this is to replace some of the letters with silver platters, or hang stockings from them. A candy cane turn upside down can be the letter j. This allows you to keep the rest of your logo very recognizable but still get a festive look. A wreath will also work for the letter "o".
Your background is also pretty simple to change out. You might want to pick a piece that is really going to match the rest of your blog template so you won't need to spend a lot of extra time changing all of your colors. In this case you're going to want to break from tradition. This could use a traditional snowflake motif but in a pink or brown color palette. You need to make sure that this isn't too busy because even at holiday time the focus is really going to be on your blog. You want to make sure that you get a white background so it really works with a more contemporary look that won't be too distracting.
Some of the simplest designs are just going to use holiday colors. This could be red, green, gold, or silver. This could just be plain. It should still be opulent to mimic ribbon or velvet to still get that true Christmas feeling. You can add in berry graphics or you can just try to use a cursive font.
It doesn't require a lot of coding knowledge to really bring this onto your blog. You can probably find ice themed or even pinecone headers. Just put this on your blog and your title will still show up. Plus it really makes sure that your blog doesn't instantly look dated on December 26th. It can even be a nice chance for the winter season.
Headers are often very specific to theme and you should keep this in mind when you choose a Christmas banner. This is going to relate to your overall niche. For a cooking blog try taking pictures of one of your own holiday treats. Plus, then you won't even have to make sure that you pay attention to copyrights because you'll own them. Try a picture of a businessman in a Santa hat for a business blog.
You could even take pictures of your kids' snowmen creations in the front yard although you should make sure that your house numbers or any recognizable features aren't shown for safety.
Start out with your typical blog banner so visitors will know that they are still at your blog. You'll need to save an extra version of this just so that you can make sure that you really turn back the clock when the holiday is over.