Well, I do it for fun (if someone reads it, then I'd even question how they found it
), mostly because I try to improve my development blog writing skills since I need to have a blog for my university related projects and I am only mediocre at them xD
In theory, it might be worth it, but it depends on what you see worth IN.
Do you want advertisment? Attention? Do you want to get players or other developers interested?
If you know what you aim for, you can modify your posts for it.
A player will not be interested in things that might spoil the game (you putting up sketches of late-game characters or showing script from any scene that isn't just little flavour text) or is "boring" (30 sketch variations of a vase in search for the right design for that apartement background). They want to be teased, feel special by seeing some things first or in development, but the things need to be cool (for example, if you make a shooter, then teasing one of the possible weapons is a good choice, but only images of good quality will interest them, not a low-poly model without any textures).
Of course, if you make episodic things, then you can always "spoil" things for the previous episode. Development Tumblrs like those from Steven Universe, Gumball or Over The Garden Wall are good examples.
If you want to use the blog for a serious career in gaming/media, then you need to do it totally different though. There is NO such thing as spoilers. They want to see your process of working, the better you document and present it, the better. Don't just show the main character, show them from all sides, close-ups, details, various expressions. Show all the sketches that lead to that one design of them. You have a background image? Show how you set the perspective up, how it looked without the decoration obejects, go full on from sketch over lineart to finished piece with moodlighting and whatnot.
Your aim isn't to advertise the game, but to advertise yourself. You want to impress people and make them interested in hiring you.
A blog in and of itself is ok, in fact it can be a very good idea.
But it depends on why you want it, what you plan to do with it. Once you know that, everything else (content, presentation) has to be made and uploaded to properly represent that. Simply putting pictures on it without considering your target audience will not make any difference (unless you have a solid fanbase, they usually are happy whenever their idol gives them something, but I assume, you're not that far [yet]).