I have a few suggestions in regard to Alistar. Now that his visuals and gameplay are in order, what he needs now is mostly story based updates. There are some other minor suggestions I have as well. Let's begin.
1. Story: in his current story, he was captured by Noxians and managed to escape. If Riot was to write a full story, I would love to see Alistar join Demacia and lead rampaging attacks on Noxus and essentially become a hero (more like an anti-hero tbh). This story could elaborate on his thoughts and how his anger and wrath affects him and his allies.
2. VFX/SFX: His Q and W (and maybe AA) certainly need VFX updates to make them look more modern (since both are the same as Pre-VU Alistar). Note how smooth and modernized Conqueror Alistar's VFX look). I like the animations, they are perfect, but the effects of his attacks hitting is what needs an update.
3. VO: I like his gruff, deep voice. Add in a few more lines if possible to give more insight into his thoughts, mental state and his personality (note Mordekaiser's VO literally stating his story and his views on death etc.). Love seeing VOs that give us a deeper look at who each champion is. Stuff like "I will break you!" or "Prepare to die" is fine as long as it is augmented by deeper lines. Alistar is one of my favorite champions and I'd like to see him become more personable to where we both fear him and understand him (think Hulk).
4. Skins: this is where people will certainly disagree with me. Now I know that recolors aren't well liked (based on ppl's statements), but I notice champs like Yi, Ryze, Morde and even Ali have skins with similar designs (but different colors, armor and weapon styles) but with a similar overarching look (consider Black, Golden and Unchained Ali). Many of Ali's skins are too heavily armored and too bulky (Although Conqueror looks great). Ali looks the best when he isnt wearing armor (Golden is a good example). So yes id love another advances recolor to add to the collection, but still have it be 1350 with new fx. For example: Dark Ice Alistar could be white with black/blue hair and beard and silver and blue wrist/waist armor (no shirt/armor elsewhere) so he is a recolor like Black and Golden but with cooler fx and a voice modulation to make him sound icy. Just my preference as heavy armor doesnt fit Ali. He is like Hulk in that way.