I have mugs, coasters, etc. from previous employers that I enjoy using, but am hesitant about bringing them to work at my current employer because they're branded with former employer's logo. Will it seem like Coke vs. Pepsi if I bring those in? What if they're not exactly competitors, or even in the same industry?
What about achievement plaques/awards? On one hand, they're a testament to your expertise and experience, but may be perceived by your current colleagues as pretentious.