Reddit mentions of Images of Japan: Vocabulary and Sentence Patterns (Exercises): For Pre-Advanced and Advanced Learners of Japanese

Tobira is a good textbook, and once you're done with it, I recommend the textbook 中・上級日本語教科書 日本への招待 and the complementary grammar/vocab workbook if you can get your hands on them. It was the book my class used when I was studying in Japan and it's mostly academic vocabulary and grammar (lots of news articles, topics on social and environmental issues, etc). I believe it would put you at a level of Japanese closer to N2 (along with natural exposure, it was enough for me to pass N2). As a note, one of the professors who wrote the book taught my class (the textbook was written for my program), but I don't really think that has any bearing on how good the textbook actually is. It's five chapters long and pretty dense, but perfectly good for self-study, imo.

Supplementing textbooks is key though, and you seem to be doing it on the reading front. For writing, I recommend using Lang-8 to make journal posts that native-speakers can edit. For listening, podcasts, Youtubers, TV shows, interacting with other high-level/native speakers. This will all keep up your exposure to Japanese and reinforce the grammar and vocabulary you acquire through your textbooks. Overall though, after Tobira you're in a good place to increase your level through more native material, depending on your goals.

If you want to pass the JLPT, I second the 完全マスター series. It's the most rigorous of the books I've looked at for N2-N1 (not sure about N5-N3, but some of my friends used 総まとめ for N3 and did fine).

If you're serious about getting your Kanji level up, I would also check out the 漢検ステップ series made for native speakers studying for the 漢字検定. I would also recommend it if you're into Japanese literature or are looking to be able to read more difficult native material. Or if you're looking for a fun challenge outside of the JLPT.